Well, check the PS90 Mini Faq
http://fnforum.net/viewtopic.php?t=4286
I think the Urban ERT 2 point sling is the best PS90 sling.
The Vest Guy makes awesome PS90 tac vests and mag carriers.
Mag Parts and MPF Tech sell rails
Hard Corps can color the gun for you if you want.
Promoted Pawn can install a laser in the stock.
The REM2 will be out soon - an LED attachment to make the white ring sight work better...
Hi Desert Dog has replacement barrels
And, there are other sponsors to choose from as well....
Many of the sponsors are here because they sell PS90 related stuff. So, Just click on the various banners. The sponsors here have slings, rails, and other stuff.