Launchers for G36's are quite rare, here on ASC or elsewhere. There are few companies that make them and not in any great numbers. When I wanted an M203 on my CA36 full length I installed a rail on the bottom and got a railed M203. Looked weird but worked.
You used to be able to import launchers into Canada since they can be legitimately used as flare guns, only the explosive 40mm ammo was illegal. A year or two ago they changed it so any type of launcher is illegal, thus making the airsoft ones illegal. There are several people who can do special orders for parts like this if you know of a site that has it in stock. These peoples names can be found in the age verified retailer section once you are verified.