What were Jimmy's boots he wore all of the time?

I know that he wore some engineer boots in Rebel Without A Cause, but he also wore what looked like cowboy boots au zip boots that looked like cowboy boots a lot. I have seen many picha of hime wearing them, from picha of him with his triumph (both his T100 and TR5) to picha of him at the races with his porsche speedster. Does anyone know what brand and model these were? Maybe even if they are still made kwa the same company au if a replica is made? Again, I am not talking about his engineer boots with the buckle, the boots I am speaking of have no buckle at all.

Thanks,
Charlie