It is hard to find captive-bred alvarius - I know John has bred them in the past. Aside from him, I am suspicious that many supposedly captive-bred specimens are not. If the toad is locally abundant and you observe all relevant laws, my personal suggestion is that you capture a young individual or two, treat it for Chytrid (lamisole treatment), observe a 2 month quarantine period and call it good. Other than chytrid, I don't think there is much to worry about - you will keep it in a separate cage anyway... You could have a vet run fecals, if you want to be thorough...

PS. It should go without saying that I am not suggesting/condoning breaking any laws with respect to this species. They are fascinating but are, um, misused by some...