Yes, Swamp Rat exists. Store Link -
http://www.shop.ratknives.com/main.scThey typically only make one particular model of knife at a time, then move on to another. ScrapYard has recently moved to the same business approach.
The Dumpster Mutt has been made in quite a large number of variations, including coated (several colors), satin, and doublecut. None are available in the store now, but seem to be plentiful in the aftermarket.
There is a very healthy aftermarket for not only the Busse/ScrapYard/SwampRat knives, but also sheaths and accessories at BladeForums.
http://www.bladeforums.com/forums/index.phpAlso, don't overlook this forum's own RainWalker for excellent Kydex and Leather sheaths. He does absolutely top shelf work. <img src="/ubbthreads/images/graemlins/thumbup.gif" alt="" />
http://rainwalker15.googlepages.com/index.html