Dive Cozumel- Yellow Rose
http://www.divecozumel.net/index.html
I know they do O2- no promises on sorb or tanks.
Protec diving- Mexico (mainland)
http://www.protecdiving.com/
Rebreather friendly listing-
http://www.rebreatherworld.com/destinations/53.html
They should have everything you need.
Inspiration Specific- (Mainland )
Steve Bogaerts (Inspiration Instructor.) Brit ex-pat.
Puerto Aventuras
info@aztecdiving.com
Website: www.aztecdiving.com
Please keep in mind that from Cozumel it is a boat ride over to either Playa or Puerto Aventuras. Give me a yell if you need any more help.
Regards, Andrew