For a REALLY BASIC belt clip "holster" that fits the 5000, I went with a Case Logic PLTK10 case :
here.
I freely admit that there's not much to it--the only retention device is an elastic band that reaches over the top of the PDA and attaches to a hook. But hey, if you want a Piel Frama Ubercase, you have to pay Piel Frama Uberprices, so I'll take the $17 Case Logic cheapie. I got mine at CompUSA; it's a good fit for the 5000, and has elastic sides, so I think it would fit the 5600 without any trouble.
I did see there a couple of bigger "universal PDA" cases that probably had space for things like cards, etc, but since my job wouldn't allow me to wear something that clunky on my belt, I went with the slightly svelter PLTK10.
-->VPutz