If you are looking for a second hand traditional kilt, you don't have to live near somewhere that might have an old rental stock for sale. This is the age of the internet!

You can begin with this very site. Check out the "For Sale" section. I have not a few kilts listed there myself, as do others.
http://www.xmarksthescot.com/forum/viewforum.php?f=23

I should also say that we, at the museum gift shop, keep a "specials" page with second hand, consignment, and overstock items, including kilts. I think I have all of our kilts listed on this site, but just in case I don't here's the link.
http://giftshop.scottishtartans.org/specials.htm

A lot of other kilt retailers will have similar pages on their web sites.

Then let's not forget about Ebay. Do a search for "kilts" and you'll find a hodgepodge of lady's skirts, non-traditional kilts, casual kilts, etc. But in and among those, you will find some actual traditional kilts for sale, sometimes at a very reasonable price. You just have to know what you are looking for. Again, you can do an Ebay search from this very site:
http://www.xmarksthescot.com/xbay.php

Lastly, you can just do a Google search for "second hand kilts" and see what comes up.

When looking to buy a pre-owned kilt, I always tell people to not be too fussy about the tartan. Yes, get a tartan you like, but don't feel that you need to wait around until you find your particular family tartan. When looking for a used kilt, you need to first worry about finding one in your size. The odds of finding a second hand kilt in your size, in your tartan, are slim. So if you find one in your size (and budget), so long as you like the tartan, don't worry about wearing "someone else's" tartan.

If you really need to have a kilt in a particular tartan, well, bite the bullet and have one made for you. But if you are willing to be flexible on the tartan choice, you can find some really great deals.
Aye,
Matt