I'm 6'5" and about the same weight and also require a size 14 rock boot. I don't consider my self obese, just 'full-figured'.
I couldn't find anything, from any vendor that was considered 'off the shelf' for my size. It seems to me all the dry suit manufacturers subscribe to the insurance size charts for their 'standard' sizes which state that according to our weight we should be 8'6" tall. The manufacturers all seem to think that XXL is 5'10" tall and 175 pounds!
Anyway, I ended up going to DUI Dog days at Wazee Lake this past summer and tried the only suit they had that worked for me, and I tested it out (it wasn't a stock size, just a really BIG custom-built one they use for guys like us). I had them measure me up and ordered a custom TLS350 from my LDS which fits great. Unless you get lucky finding a used suit you may have to go the custom route.
You may also want to be aware that with a size 14 rock boot, you may not be able to use your current fins. I have XXL Atomic Split Fins and no way did that rock boot fit in the pocket. I looked around and the only thing that I could find to fit were some XXXL Turtle Fins. I got them with add-on spring straps and they work perfectly with the bigger boots.
Good luck!