I'm sure you'll get many suggestions but look at National Sails Supply. I've been very happy with price, quality and support. 

Richard;
Just a few thoughts; First, the TIDES sail track is a device that is placed in to the sail track slot in the mast and makes raising and lowering the sail MUCH easier. We have one and I would not be without it. Added years to our sailing life. You will have to add cars to the sail but well worth the money and effort. Reference; ​
https://www.tidesmarine.com/sailtrack/intst_overview.php 
Sails . if you are looking to buy used, then National Supply is a good place to start or you can look in the 'classified' section and find some one who is parting out a similar boat.
Bill

We replaced the original Main and Genoa last year and went with National Sails.   Our last 2 boats used North Sails, but I started looking around after disappointing customer service.  
I ended up ordering a custom sail instead of the standard Catalina 36 sail.   That said the price was less than half of North and Ballard sails.   

The sails are nicely made and the detail work (leather patches, ect.) is better than North.    

The main has double reef points and custom locations and I chose not to have sail numbers or the Catalina logo, but they are available.   

Shipping was to my door within the quoted time.   

I attached a couple photos of the old and new main.   Our old main is slowly becoming grocery shopping bags that we give to friends.

Good luck with your choice.   

Ray

Do contact Chic Lasser.  He is the rep for Mack Sails.  I purchased a new jenoa in May and he was extremely helpful.  Mack has a flaking system too that had I needed it I would have definitely checked it out.  Prices were very competitive and the service was great.  Chic helped get my sail delived to my front door in a short time frame to enable us to go on our trip.  The quality of the sail is very very good!   Quality material and workmanship.   Should have ordered a main too, but will do so in the next year or two.   Chic is listed in our directory.

 Bill Taylor
#1612 Standard rig
Washington, NC
 

We replaced both sails on our '98 MK II this past fall and went through Chic Lasser and Mack Sails.  Chic was very attentive to our needs and we spent a lot of time on the phone to discuss the type of sailing we do, where, and what our options were.  We also spent time talking with Doyle.  In addition to the sails, we went with the Tides sail track.  Unbelievably easier.  Finally, we added the Mack Pack system.  Some of the issues we considered were 1)  Mack sails are made in Florida, while Doyle are made off shore;  2) The  Mack headsail was bias cut vs a slab cut on the Doyle; 3) Mack used a premium sail cloth as standard, which would have been extra with Doyle: and 4) cost.  Chic offers a discount for 36 Owners and the more you buy Mack offers additional savings.  In the end, The Mack sails were substantially less expensive than with Doyle.  I have been told that folks like National use a cheaper sail cloth that is not as durable and not as well stitched and also made off shore.  I believe, with  sails, you do get wht you pay for.  It depends on how you sail and how long you plan to keep your boat.  The performance of our boat with new sails in speed and pointing ability is beyond what we expected.  Give Chic a call.  If you want to discuss this more, contact me outside of the forum.

I replaced my main 2 seasons ago with one from a local sailmaker here in Michigan, Kent Sails.  Thrilled with the result.  The Dutchman system seems to be a love-it or hate-it system.  I for one hate it.  I could never get it "right", I was constantly adjusting it to try to get the lines in the right position, and by the time I got it tweaked to where I was happy with it, the season was over and I would repeat the process the next year.  I went with a stack pack system with lazy jacks, and that is 1000x beter in my opinion.  I also installed the Tides system, and it has made all the difference when it comes to raising and lowering.  Highly recommend.
 

I have the roller track system on my mast. It is wonderful.  Raising main sail is like cutting  through butter with a hard knife.   Ditch de Dutchman.  POA!   Before we put away the main, we drop the first 3 feet and put in the first reef.   This is of course the biggest of the folds, and then you can easily drop rest, alternating sides.  The benefit is also that next time you come out to Saul and have high winds, the first reef is in.