Nick,
Glad to hear that you were able to fix the problem with minimum bending.
The rollers and rivets (pins) are available online and are easy to replace, exactly as you wrote. The pins were originally riveted in place with a rivet press (which can be purchased), but a gentle squeezing of the very end of the rivet with a pair of pliers will do the job. Squeeze just enough to keep the rivet from being able to be pulled out, but not so much to keep the roller from spinning.
 The rollers and pins can be replaced without removing any parts from the transformer.

Larry