I carry on my bike, the same as in my truck.
A Ruger LC9 in a Crossbreed hoslter,strong side,which helps on the bike as I'm left handed.
And my LCP weak side back pocket.
In 45 years, I've never had anything fall out of my pocket while I'm on my bike.
Hmm, back pocket carry might not be a bad idea. It may be a little easier to access while on a motorcycle than a pocket holster in a front pocket (when stopped anyway). Since most attackers would probably be robbing you, the motion to your back pocket could pass as you going for your wallet. Unfortunately, my favorite advantage of pocket carry would be impossible with back pocket carry (the ability to put your hand in your pocket and on your gun without brandishing or drawing extra attention if you think there may be a threat but you aren't yet 100% sure), but on a motorcycle it wouldn't really be feasible even if the gun was in the front pocket so that might be a good option.