For those with higher-powered airsoft replicas, these products at Airsoft Extreme can help you... "FireFly Hopup packing and bucking. 3 types of packing for TM pistols and spring rifles. There is Hard, Soft and Extra Soft. We also have the Hard Hopup Bucking for high powered AEG's."  These are made for TM AEGs, GBBs, and spring powered rifles so make sure you install them on TM compatible ones.

Firefly Hop Packing - Extra Soft

Firefly Hop Packing - Hard (for VSR-10, TM Pistols, etc.)

Firefly Hop Packing - Hard

Firefly Hop Packing - Soft