If you measure the number of studs the PCD centre bore diameter and stud diameter these may be able to help you
http://www.rphleisure.co.uk/
If you speak to a guy called Rob, he seems to be the one that knows
They have just got me some new wheels and tyres for mine admittedly that's a uk trailer but most PCD's are Imperial based anyway, mine were 5 stud 6" Pcd