If you want something inexpensive but good quality, you may want to look at Bulldog holsters at a sporting goods store near you. You won't win any beauty contests with a black nylon holster, but they are pretty secure. And the straps are, of course, adjustable. It may be heresy, but Ruger sells quite a few in the online "Ruger Store". Different gun, but I found a nice 6" holster that's made for the 6" GP100 that fits my 629-6; these are virtually the same physical sized guns. Now, if you want a nice holster and have some time to wait for quality, 6-12 months, maybe, which isn't bad for the one I got, but don't be afraid to check out Barranti Holsters/Leather products online. I can't remember, but I think they may have had some popular ones already made up...don't quote me. I have found nice used ones for sale right here on the Forum Classified Section. I found a couple of those old school basket weave holsters that look like they came from some old black & white TV show.
For a heavy barrel M10, one made for the SP101 Ruger may fit.