First of all, the four hole wheels aren't new, just different. The five-hole wheels are rated to carry more weight
Second, likely you do not want automotive wheels because they are likely to be hub-centered and the trailer hub is likely designed to be lug-centered. That makes a difference in centering the wheel and also may make a difference in the proper cone angle on the lug nuts themselves (Many hub-centered wheels use a zero or flat angle because the hub does the centering).
As Brian said, if you can't find the right wheels at a bigbox store, then order them from a tire store.
To answer your question, however, likely your rims are 5 on 4.5" which is a popular size for Ford and Chrysler products, so if you want an emergency rim, that would be what to look for.