Your inquiry brought the following idea into my head....
On the back of the cart, a classic old west shipping crate, labeled Winchester repeating rifles or some such. Open the hinge lid back (towards the front of the golf cart), and two uprights hinge up from the ends, and then a cross piece installed between them with long gun barrel rests. In my vision, the crate would have enough room to store the long guns and a bit more when closed up and be locked up.