In addition to continuing to search, there are two other options you could explore:
1. Rick Herrell is a great machinist who could make a custom tool rest for you. You would need to provide detailed measurements for your lathe - if interested, contact him to find out what information he needs to know. He made a replacement tool rest for my first lathe and it was a beauty - - almost too nice to use!
2. You could make your own. Rick Morris has several YouTube videos (search for 'Rick Turns') on making toolrests using common materials purchased from hardware stores - mild steel rod and angle stock. H shows that the best way to attach the crossarm to the post is by welding or brazing, and if you are set up for that process, you could even get fancy and add a tool steel rod at the top of the crossarm. I don't do either and I'm not particularly interested in learning that new skill, so when I made a 3" tool rest, I opted to drill and tap a hole in the post, and attach the crossarm with a screw and lockwasher. That arrangement has worked well for me, but I think the fact that the crossarm is only 3" means that joint doesn't get stressed excessively, and I'm not sure it would be a good way to go if you are making something longer. And because the crossarm is mild steel, I do have to periodically file away nicks (but that's part of routine lathe maintenance).
