This is an informative post.
I have been looking for test bench rollers for Standard gauge for a while now.
They are available through Jak Tools.
They do not have them online on a website, but here is the information you need to order them:
Orders are placed over the phone:
609-664-2451 Extension 102
Ask for Jeff Kinsberg
They accept Visa and/or Mastercard
They offer a set of 4 for $115 plus $15 shipping.
I just ordered mine today.
I hope this helps others like me!!
Mark