These are pretty easy to come by. When I experienced my first motor weirdness (jutters and no power) I immediately tacked a few of them on to an order I was going to place with DigiKey anyways. In single quantities, they're $1.46 (CDN!) each.
Turns out I didn't really need them (the problem was with a bent pin in the connector), but at least I have them in hand in the event of a future failure.
Speaking of problems with connectors... The same thing that happened with the Hall sensor connector (pin bending outside of the connector) happened today, but with the throttle connector. This time, however, the offending pin didn't go outside of the connector body - it went into the same slot as its neighbour - in this instance, effectively shorting out the throttle.
When I powered up (I've added a power switch to the controller), there was a pregnant pause while the microcontroller booted up... THEN the whole bike shot across the floor at lightning speed (full throttle, no rider). Miraculously, no damage done to anything - but it really has me paying particular attention to the feel of those connectors as I'm pushing them home after a disconnect... I was so stunned by how fast it took off that I stood there for a full five seconds just watching the wheel spin (the bike "wheelied" up against a stand that has a thickness planer on it and fell back on the rack holding the batteries, the rear wheel staying off the ground). I feel like I got away with one, there...