C/D/N Isotopes also has an office in Canada:

C/D/N Isotopes
88 Leacock Street
Pointe-Claire, Quebec
H9R 1H1
CANADA

Tel: (514) 697-6254, (800) 565-4696.
Fax (514) 697-6148.

They specialize in labeled organic compounds. I do not see enriched CO2 or
carbonate in their catalog.
-Dan

Dan Bryant
E-mail: [log in to unmask]
Home page: http://geo.princeton.edu/~jdbryant/
Tel. (609) 258-2612; Fax (609) 258-1274
Department of Geoscience
Princeton University
Princeton, NJ 08544