Try this site, they have cross references for bolt patterns used on cars:
http://www.discountedwheelwarehouse...._Reference.cfm
I went to the local junk yard once and pulled rims and good tires(the
spare)from a wrecked Plymouth Horizon (bolt pattern 4X100 13"). They
only charged me $10 per tire.

Gary Carter wrote:
I have an older Cobra trailer (1980ish - aluminum) and need to find another
tire rim (I had an axle mishap and lost one of my tire/rims). The rim is a
4 x 100 metric (four lug holes and 100 mm between each lug) and supports a
13 inch tire. Does anyone have a rim for sale or can suggest a source in
the US hopefully close to Atlanta, Georgia to get one?

Thanks for your help.
Gary Carter