Or buy a used bongo and have it defretted. Might be the easiest option besides waiting for a new BFR or vault release. Or search the used market for a fretless bongo.
Used market is cool. You can find discontinued colors and discontinued PU configurations, as well as the piezo bridge which is the ultimate for FL.
Example of shopping used market:
Mine are both single humbuckers with piezo. With piezo you also get 4 band EQ, rather than the 3 band thats normal for the single humbucker.