I've been enjoying my 642 for a couple of years now.
The holsters I use most often are the Hume JIT, and the Ken Null SKR.
The best loaders I've found are the Jetloader and the SL Variant (no longer sold in the U.S. I think. At least the only dealer I knew of sold out and wasn't going to carry them anymore - supply difficulties I think).
I also use a Bianchi speedstrip if I need the flatness for concealment.
For ankle carry, I've only used the Uncle Mike's ankle holster.
It's okay, but my problem with it is the strap cuts into my ankle too much.
Other than that, it holds the gun securely and allows a good draw.
I'm still planning on trying a custom made ankle holster and have narrowed it down to either a
Ken Null,
Bulman,
Tauris,
Alessi,
DeSantis,
Don Hume, or perhaps a
Bianchi.