Any suggestions for a holster for a P90 Ruger,shoulder or hip?

The semi-generic nylon holsters from Uncle Mike's are cheap and work well for me.

I also found that their new "Kydex" is a pretty good holster. This is one of the hard plastic holsters that the gun snaps into. You can get a paddle-style for concealed carry, or the usual belt loops. The paddle holds the gun higher and closer to the body and that's my preference.

Try this, I like it with the optional magazine holder, but there are a few others elsewhere on the site.
http://www.cabelas.com/cabelas/en/templates/product/standard-item.jhtml?id=0012800223329a&navAction=push&navCount=3&indexId=cat20776&podId=0012800&catalogCode=ID&parentId=cat20776&parentType=index&rid=&_DARGS=%2Fcabelas%2Fen%2Fcommon%2Fcatalog%2Fitem-link.jhtml_A&_DAV=MainCatcat20712&hasJS=true

I have 2 holsters for my P-90 and both of them are made by Uncle Mikes. One is the nylon paddle style holster (it's ambidextrous too) with a mag pouch on the front and the other is a police style holster I use for duty as an armed guard.