Well, I learned something today - thanks guys
I've never found Mopar parts on Rockauto before.
When looking for parts I enter Jeep, 1997, Wrangler, 4L, then the part I'm after, in this case Cooling, Thermostat.
I've never seen the option for Mopar parts pop up doing it this way, so just assumed they weren't available on Rockauto.