You can try contact cement. That’s what I’ve used in the past with partial success. I would estimate half of the velcro strips stayed on the diffraction pads after pulling the grills off to test for adhesion. Basically, it’s a one time deal though. Use the cement, put the grills back on, and don’t take them off until you’re ready to replace the diffraction pads. I applied the cement directly on the back of the velcro and push them back onto the diffraction pad (I used the old velcro strips, not new ones).
