Sealing a hole

A few months ago I discovered water soaking the carpet inside a linen closet in the bedroom of my fifth wheel. I dried it out and have since been through several heavy rains with no water intruding. No seams or anything on the outside but I think I've finally found it. I measured off the distance from a window to the wet closet inside and it aligns with the forward awning mount. As I've now found, the wiring for the awning motor comes out of a hole at the bottom of the bracket and runs up under a plastic race. There is a half inch hole where the wire comes out and it isn't sealed. From the timing, I think it happened when washing the trailer with a pressure hose.

So, after all that, which is surely more than anyone cares about, what is the best thing to seal the hole around the wires? I don't know if should worry about making sure there is some give for the wires or not.

Thanks.