I've been a lurker here for a while, but being a huge Stargate fan, I had to register just to help you out.
This site should give you what you need: SG Costume Guides.
What you've currently got most closely matches the SGC Woodland Uniform. It's difficult to find a reference picture for that uniform variant, since it's not used as often as the other variants, but that site will break down the uniform and list the various parts.
If you're interested in the weapon, Stargate teams use the FN P90. It should be relatively easy to find reference pictures for that if you're going to construct your own, but you can also probably find a paintball gun that uses the FN P90 stock, as well.
However, if you want to get really technical and and don't mind building yourself a weapon, I recommend taking a look at the "Carter Special
." It's a gun that Samantha Carter specifically created for the SG teams and, if you've got that, I'm sure your costume would be quite a hit with fans of the series.
I hope this helps you out.