I am kind of in the same situation with my stereo equipment. All i did was go to totem and picked up some aviation wire (1/8 of an inch diam. or so), made loops on the ends, and locked it with a pad lock to the strap loops on the floor.
Seeing that you are using a golf bag, you could probably use a thicker wire, since i was restricted to size becuase of the screw holes on my amp. But luckly an amp is a little more hidden than a golf bag

It could still be stolen by someone prepaired, but i suppose a prepaired person could probably steal just about anything anything.
Brad