I'd advise against a thigh holster, because unless your running around kicking in doors, and such, it just gets in the way, and is a pain in the rear.
I carried my M-9 in a thigh rig for most of Iraq, and it got in my way alot.
Also, I dont know of many good thigh rigs for the Witness.
However, if you do decide to get one, Blackhawk, isn't that great of a company, they have alot of QC issues, soem holsters are good, my thigh rig, works like its supposed to, but the newer ones, i.e.
the serpa, has had some known issues, and gets gummed up and can be jammed fairly easily. The Safariland holster is IMO a much nicer holster.