In case anyone is looking for a good source for DR0141TX rootstock seeds, I was able to buy some from Paramount Seeds. They were cheaper than any other source I found, so I decided to grab some and give them a try against the RST-106 rootstocks.
https://paramountseeds.com/product/d...rootstock_raw/
They carry several other rootstocks as well including Maxifort and Estamino.