I too, wanted the convenience of the leather holster my 7290 had. I have the OEM RIM holster as described above, but I don't like having to remember to pull the flap up to reholster. One day, I will forget and let go of my Curve, sending it to an LCD cracking concrete surface below.
I've also tried a sleeve holster (from eBay) that works well. The concern is retention, however, as the Curve's straight body doesn't have the friction-fit benefit of an inclined draft-designed case of the 7290.
I found my low-profile solution from Seidio, which offers a holster with minimal obtrusion and excellent retention. Check it out.
http://www.blackberryforums.com/gene...-8300-a-2.html