They show up on the bay every once in awhile, or you can just scratch one. Not hard at all. Have a look at what M.C. Fujiwara did in N-scale on his Summer Shunting Project layout. Just scale it up and you're set. I'm going go be doing one as well, but I'll be doing it out of wood instead of styrene.
Not sure where you're seeing $300, there's an HO Walthers kit for no reserve bid now at $22, bid concludes in 2 days. The buy it now offers are higher but still not $300.
mmm.. you are correct, I went back today and couldn't find anythign on $300 makes me wonder if was from the uk or another country.. I did see the apron for $200 and the other carfloats for 22 and 25 or somewhere around there, much better! probably should switch to decaf!