Found this info available at the Carlisle Tire website......
http://www.carlisletire.com/product_car ... erence.pdf
Lots of good info here about wheels and tires.
They have several models of a 13" wheel with a 4 on 4 bolt pattern.
May fit the harbor freight trailers.
(dont know about frame clearance on Harbor Freight trailers but seems to be a common question.)
lots of wheels to fit 5 x 4-1/2
good tire info too.
I am not connected with Carlisle in any way........thought this might be useful to someone.
Have a great one.
Walter