FIEIL 2 Pack Breathable Universal Shoulder Pad, Silica Gel Backpack Strap Pads, for Shoulder Bags, Guitar Strap, Detachable Shoulder Strap Pad Pads Help Relieve Shoulder Pain(Anti-Slip Texture)

Darn. I have used belts with Gatekeeper attachments on bags with tri-glide mounts. The tri-glide is mounted on a simple loop and the Gatekeeper can slip in without removing the tri-glide. Tom Bihn and Gossamer Gear make some excellent belts. That would require some sewing. I agree that slim should pads would be the best bet. I used some like this for a shoulder strap project. They may be a bit narrow but will sit securely on the webbing: https://www.amazon.com/dp/B0DP1YPMVD