I have been riding with a Ruger LCP II. I prefer strong side front pocket in a self made Kydex holster. Next would be strong side back jersey pocket. Last would be handlebar bag with the zipper partially opened depending on the terrain. I have a thong attached to the magazine for security.

A top tube bag will hold my pistol but I keep repair tools there. A top tube bag might be a good spot for many riders.

My 10 MM pistol friend hasn't been riding with his pistol. My .22 LR has to pick up the slack.