Well, if you go with a nylon sheath, it shouldn't be too hard to sew on a loop for a flashlight. If you want to add a small folding-knife, I'd recommend going with something small and with a pocket-clip, preferably slim-profile (such as a gerber paraframe or something similar--there are different models like that). A prybar? I've seen some small,
slim ones. You could probably add a loop (or pocket) on the back of the sheath and slide
it right in. If you decide to try and sew it, I'd practice first on an old, junk sheath you'd
throw away, and I'd also recommend good nylon thread. (Also a thimble--I know from experience, drove a needle through my thumb AND through the nail..) I've worked a long time (years) at modifying sheaths. I've come up with all sorts of ways (some effective,
some not). If you use the loop method, make sure there is a bottom on the lower loop,
to keep the item from falling out. I will recommend, though, adding a ferro rod (covered),
as those can come in handy and they are also fun to play with.
As far as production sheaths try: survivalsheath.com They seem to have a wide-variety and many products. There's plenty of eye-candy and information. I hope I helped. Good luck.
DS...