Most plug manufactors will list them in there application catologs.(champion ,ngk,ect...)Just go to your local auto parts dealer and ask for them.they should be free,we give cats away all the time to customers.Theres also a lot of good info on what all the numbers stand for on the plugs(temp,thread,electrode,reach ...) Perhaps a small engine dealer can help also.But make sure to ask for all cats,NGK will seperate auto and non-automotive in separate cats,TB