Unfortunately the G36 serms like the red headed stepchild of Glocks.
I just got an OD framed 36 in a trade and I've had the same experiences as you - wait until you look for magazine pouches. Other than the overly large fobus dual mag paddle job, there are no major manufacturers making them for the G36. And I'm a lefty to boot, so I had to get one from one of the custom kydex places.
Be careful about the + extensions for the 36. Most of the things I've read about them (here and other forums) bring to question their reliability and the general consesus seems to be that they should only be used at the range.
Bad news about the slide stop - I live local to Glock and when I took my 36 to them for inspection and upgrades, I asked for an extended slide stop. The armorer replied that Glock doesn't make them for that model. However, I was able to get factory night sights for something like $67 installed.
On another positive note, I got an idpa holster for $7 on clearance. Guess there's not too much demand for lefty G36 OWB holsters.
Also, an IWB holster wasn't too hard to find either, though I haven't tested the gun enough to carry yet.
One other thing - I HATE the Glock serratred "target" triggers, which the G36 has, and of course there's no smooth trigger available from Glock either. Fortunately, Overwatch Precision sells a version of their Falx trigger for the 36, and it's a great trigger .
Sorry, I realize I'm kind of all over the place in my response, but I hope at least some of it helps.
-bob