Spring Power Revolvers do exist, they are just not practical for anything at all, plinking target shooting or even as a paper weight. Due to their design their FPS outputs are extremely weak, so finding a spring based revolver that can out more than 300 is extremely unlikely.
Currently, no Canadian or even foreign retailers stock such an item.
If you are interested in something for "target practice" then I would suggest sticking to the air gun / pellet gun route instead of the airsoft gun route. Simply because they are easier to acquire and are more suited for "target practicing".
"Its only a little bit on fire"