In my standard large size P320 grip module there is a half moon cutout about 2 inches long toward the rear of the magwell, to the rear of where the magazine "back side" would go. It looks similar to the X-Five Legion area where the added weight goes. It doesn't appear to be made for a weight to go in and click in like the X-Five.

Is there a weight that fits it? Or is there a way to modify a weight to stick in?

Hello, there is no weight for the standard P320 grip module, nor was it intended to ever have one. There are no 'ledges' in the P320 grip channel to retain a weight even if you made one to fit.

The channel in the X-Five grip module, as you have noticed, is very different.

Could an adhesive automotive wheel weight be inserted into the void? The lead could be trimmed/thinned as needed.

Looks like you can purchase the X grip frame, which handles the weight as a design feature.

quote:

Originally posted by az4783054:
Could an adhesive automotive wheel weight be inserted into the void? The lead could be trimmed/thinned as needed.

A better option that would get more lead into the void would be to pour lead shot into the void.
Then seal off with fast setting epoxy.
Use a small shot size like #8 and make sure that the far end of the void is sealed off before beginning.