I remember when they were available in the hobby back in the days as wild caught imports, haven't seen them in a while, and my LFS just brought in some captive bred from Asia.
Love these.
Some whiptails are being bred in such numbers here, there prices are comparable to bristlenose.I bought 2 x 5-6cm (2") for about US$1.65 ea.
They are perhaps better cleaners than bristlenose IMO. I use them singularly and not in shoals