I did some more reading and learned a couple of new things. Rifaximin (Xifaxan) is indeed a newer treatment for SIBO, and the treatment course is much shorter than my older experience. I consider this great news (except for the price of Xifaxan). However, the breath test remains a bit of a problem: a positive result seems to fairly reliably indicate SIBO, but a negative breath test doesn't rule out SIBO. In some studies the breath test only turned positive in about one-third of SIBO cases.
Interestingly, herbal therapy might work as well as Xifaxan. The specific herbal therapy studied was "2 capsules twice daily of the following commercial herbal preparations; Dysbiocide and FC Cidal (Biotics Research Laboratories, Rosenberg, Texas) or Candibactin-AR and Candibactin-BR (Metagenics, Inc, Aliso Viejo, California) for 4 consecutive weeks." Here's the article: