Amy, anything pre-1960 is going to be tough to find, especially if you want a decent runner... and at that price, it might never happen.. Keep your eyes on here, Ebay (where I found mine), guns and rovers, search craigslist nation wide and search on all of the independent rover parts places, alot of them have "trucks for sale" sections.
Spread the word that you're looking and you'll find something. I'd drop the pre 1960 thing though, and stretch it out to 1970 or so, you'll have alot more luck.
~Steve
---- 1969 Bugeye ----
---- 1962 Dormobile ----