So you have a Full Circle, in 1/4-20 size, not yet installed, and you want to have a second set of 1/4-20 adjusters, or at least one non-pickup adjuster, so you could move the Full Circle off the bass it's not yet installed on, at some indeterminate time in the future? As noted, at least in the US this is an extremely common size, I'd contact a Fishman dealer, or Gollihur Music (who are a Fishman dealer) and ask about this. The unthreaded size needs to be the same too.
But frankly, if I were to install a pickup on one bass, a pickup that's kind of time consuming to install - and then I wanted the same pickup on a second bass - I'd probably just buy another pickup of the same type.