Cats8 ~ Service Caster Corporation website. Choose "chair and furniture caster" category. From there you will see links to how to measure caster stems, a phone number to call or you can send a sample of your existing caster for them to identify. The type that we bought is called Softech. It's hardwood floor safe with thermoplastic rubber tread. You can choose wheel size, etc. DH talked to Bradley Rhodes on the phone.
We did not make any alterations to the cabinet. They popped right in.
Izeider ~ In all my web surfing, I certainly didn't see anything about Amish cabinets, but they probably don't do the internet, so not really any option for me. We did not add anything, just replaced the casters with softer ones for our flooring. We did order locking ones.