No, add-ins are now freely available in JMP Marketplace, but Bayesian Optimization is a core feature of JMP Pro, so it can't be bought "separately" as an add-in.
There was a Bayesian Optimization add-in (archived link) done by @yuichi_katsumur and freely available some time ago before its integration in JMP 19. It doesn't seem to be available now, as add-ins have now migrated to the JMP Marketplace.
Victor GUILLER
"It is not unusual for a well-designed experiment to analyze itself" (Box, Hunter and Hunter)