B and B heres a link for gunsamerica.com. I went there and just typed in a search for the 257 Roberts they have afew new and used guns in this caliber and if you dont mind doing some internet shopping getting the gun shipped then here you go. You can at least check out some models of the gun you may not of thought of. Good Luck. I like the 257 Roberts myself and saw a couple on here that looked pretty cool.
http://www.gunsamerica.com/search.cgi