Concealed carry on horseback is problematical. It’s really problematical if the device is a fanny pack or other object where access is already difficult.
One possible compromiss is a shoulder holster under a shirt or jacket. It’s quite easy to reach accross the body and draw the weapon. If a shirt is worn, make it a Western shirt or some other style where the closure is a snap, not a button. As you reach in to draw you can “pop” a couple of snaps loose by just opening your hand a bit and draw the weapon with a reduced risk of “snagging” the shirt material.
While astride I don’t like to carry concealed. With concealed carry there is always a risk of snagging on clothing. Add a possibly jigging horse and a rider who has not practiced using the weapon and you’ve got a real recipie for problems.
Since I’m left handed I’m modestly ambidexterous and can shoot with either hand. I have more carry options. My preferred way is a left handed cross draw. The pistol rides one belt loop to the right of the belt buckle, just in front of the point of the hip. This puts it far enough off to the side that I don’t get jabbed by the butt yet is not too far to comfortably reach.
Before you even think about carry while mounted GUN BREAK YOUR HORSE!!!
Then figure out how you want to do it and practice, Practice, PRACTICE!!!
Carring a weapon means carrying moral responsibility.
G.