the main issue for you will be indoor/outdoor switching... it can be a bit of a hassle to swap springs, but if you can get it exactly to 350fps, it's not a terrible disadvantage to the tweakers shooting closer to 400. That's really the only advantage of a gas gun in your situation, the npas doesn't need the whole thing to ripped apart to get to the spring.
the KA m4 is the most popular starter m4 in canada currently. Almost every retailer in canada has it. You are not looking for the right thing if you can't find it. Sadly, it's the policy of this forum that links to gun vendors are not permitted outside age verified areas. So if you get your AV, we can tell you everything you need to know.
On the other hand, if you can see the ads on the forum... well... there you go.