Nilo can also supply you with unicorns if you happen to be in need.
As well as open mics and music shops, rehearsal studios generally have a noticeboard with personnel wanted ads on it.
Bandmix and JMB are both horrible to use. Bandmix is a good concept spoilt by the morons that simply tick every box for musicians wanted, so 90% of the bass player wanteds are also accordion wanted, triangle wanted, percussionist wanted. JMB's search facility is about as good as Amazon's and AliExpress's. That's not to say you can't find bands that way (I have), but it's a very time-consuming and frustrating quest.