I am having my doors rebuilt and reskinned, and one of the rollers is broken. I found Crown Hardware in South SF and am headed there now, but if anyone knows of another/better option please let me know. Thanks!
Stanley / National were the original manufacturers and they still make them. Search for barn door hanger / trolley OR box rail hanger / trolley.
I have ordered some for my door and will post here on how they work out. My cost was $105 (for 2 pairs). I ordered the one rated for 600 lbs per pair (national part number 5087).
I am in the process of automating the garage dooors and decided to change out the hangers since the bold threads are mostly worn out and not much adjustable any more.
***Update from my previous post***
I have replaced the original door hardware with replacement hangers. Many of you have ordered replacement part from Crown Industrial in SF. Not one to make it easy on myself, I decided to search around and ordered mine from A&H Turf Specialities online. The Stanley/National Part number is 5087. Good news is that it works perfectly. It is also only half the cost and is rated at 600lbs load per pair. Bad news is it is a special order item and takes a month. may be mine was delayed due to holiday season.
I have also automated both my doors thanks to ideas from Tod and OSUNICK. I used Sommer Sonoris 550 Openers. They were very easy to install and completely silent. They are a bit more expensive than standard openers but a cinch to install and work like a charm. I will post details and pictures soon.