Not as far as I can tell. I've seen a few of Supro's guitars at GC, but not the basses. In fact, GC's web site doesn't even mention the Huntington bass; neither do Sam Ash,
Sweetwater, or CME. I found a mention of the Huntington I on Zzounds, but they say it's no longer available. When I look at the list of authorized Supro dealers on Supro's site, the only ones in my state (California) are 400 miles away in Los Angeles (and all four of them are Sam Ash stores, so how likely are they do have something that their own web site doesn't list?). So where can I try out one of these very interesting basses without simply ordering one on faith directly from Supro?
Also, one question I have about these basses is, how noisy are the gold foil pickups compared to, say, a stock Fender Jazz or Rickenbacker 4003? I found both of those pretty annoying until I replaced the pickups with noiseless ones (Lindy Fralin Split Coils for the Jazz and JBE humbuckers for the Rickenbacker).