Have you tried Fisheries Supply in Seattle?

I've done the masthead replacement from MarineBeam, and am still working on saloon lighting.  Their quality is very good, and the circuitry also allows for voltage variability, which prevents outages 50 feet in the air. https://store.marinebeam.com/  
I replaced the entire masthead fitting with the white plastic one they sell, but was disappointed by the quality of that fitting.  The tri-color bulb itself (which is 95% of the cost) was wonderful, but the plastic fixture shattered with the first cold weather we had: ​https://store.marinebeam.com/smart-led-tri-color-anchor-light-and-strobe... .  They were excellent with customer service, and sent me their version of the Schedule 40 masthead light, which worked perfectly. https://store.marinebeam.com/all-around-led-anchor-light-for-sailboat-ma...  Personally, I would order this superior fixture with the tri-light bulb directly.
Both take an indexed bayonet bulb (BAY15d​), and aligning the bulb to the masthead is a challenge; much easier if your mast is down, obviously.  I found that doing this in semi-dark with a test 12V battery made the alignment much easier.

For the twin-bulb saloon lights, which are also bayonets, MarineBeam suggests their 'elevator' bulbs to get the correct distance between the top and bottom of the fixture (​https://store.marinebeam.com/15-led-1383-and-1385-r12-elevator-bulb-2w-b...) , but this is only white.  They do sell a red-white switchable with a bayonet (​https://store.marinebeam.com/9-led-bayonet-reader-red-white-switchable-b...) but it may not work with the distance.  I've not tried replacing this yet.  Personally, I'm thinking about ditching the entire 'eyeball' fixture and going with a more disbursing dome light as I do not need directional lighting.  Tell me what you think of something like this for the center saloon light: ​https://store.marinebeam.com/surface-mount-led-fixture-with-dimming-fx-y...

The MarineBeam tri-light has a double contact at the bottom, indexed side, so it will only fit one way in the holder.  There are some minor adjustment screws (eyeglass-sized screws) on the bottom of the bulb itself to allow alignment, but it's not something that I'd try dangling 50 feet in the air!  Loosen the screws and rotate through 30 degrees or so. You can remove the screws (eek!) and move the entire top of the bulb to the next sector and re-attach. You can imagine the wire sizes used inside a 1-inch bulb, so don't move it around too many times.  I was 'lucky' that I was replacing the entire fixture, so I could move the fixture around on the masthead prior to mounting and only fine-tuned with the bulb adjustment.   If you have specific questions, I would call MarineBeam -- they're a relatively small outfit and the customer service person actually found a fixture and measured it for me while I talked to him for ten minutes.  He could not have been more helpful, short of flying out and mounting it for me!

The problems with alignment are two-fold: First, to insert the bulb you press on a spring and rotate through 15 degrees to engage the bayonet.  This means you need to install, mark the change you need to make, uninstall, change, then re-install to check.  Remember to tighten the adjustment screws well because you can shift the top as you press to install the bulb. Second, you are trying to align the red-green sector division with the centerline of the boat, which is not easy when you're looking only at the masthead. A small angular deviation will give a large distance at 1 mile. Even with the mast off the boat, it was difficult to look at the bulb and align it with the mast.  With the bulb on, however, it was easier to see the colored sectors.  BTW: the bulb is not marked with what colors are shown, so you need to turn it on first, and mark with a sharpy or something which are the red-green-white sectors.  The pain is worth it, however, as I now have a anchor and tri-light that will outlast the boat it's mounted to.

As far as cabin lighting, my problem with LED's is they give off much more light than I really want in the cabin for almost no power.  With all the light sources in the C36 cabin, mostly spot lights, I have a difficult time turning it down enough to have a mellow overall light.  I generally have a couple of the bulkhead spotlights on, pointed back at the bulkhead for indirect lighting. A dome light at the top would have been better.

Hi,

Just be aware, led's can cause a lot of interferences on tx/rx transmissions. If you have AIS onboard, just watch at your MFD, showing AIS targets with/without your led lights on/off. You will be amased how some led's can interfere...

Best Regards.