I don't know about Texas multipliers, but Southern Exposure Seed Exchange usually has potato onions in stock until mid Sept, then they sell out.

Your local Craigslist would be a good place to ask for a local strain.

Thanks for your help. I found them on Jobes Gardens. They are a very old variety. I ordered a half pound and got 35 onions and they are really big in clumps of about a dozen. I already had evergreen bunching but wanted these because my family had them for generations and as my dad got older they died out. I can't wait to see how they grow here. Wish me luck!