If it's legit, buy it. It sounds like it does check out as legit.
You care enough to check into it in the first place, so you want it.
Now, think about how much money you spend in one year, on various things you never even remember.
Next January, you wouldn't miss the money, but you'd absolutely still appreciate the holster.
Have you spoken to the owner of the holster about it? I know one angle is to keep him in the dark and talk him down, but if he's a collector and not just making money, then he'd probably understand the situation and might work out a deal, a swap for something else in return. Even the most flint-hearted might say "I usually don't do this, but.....". Maybe offer to buy him another in good shape and do a straight trade.