Hyper Shilver (Fusion with Shadow and Silver) by ByGhostEduard on DeviantArt

Sonadilver, Shipping Wiki

Sonadilver (Sonic Shadow Silver fusion) by TheLegendarySonic on DeviantArt

Hedgehog Fusion - M.J.K. - Wattpad

Sonic/Shadow/Silver fusion Sprite Sheet by Danny -- Fur Affinity [dot] net

Sonic + Shadow + Silver Fusion Mask Products from grunty art

A Problem of Paradoxical Proportions - Chapter 1 - stagemanager, tharkflark1 - Sonic the Hedgehog (Video Games) [Archive of Our Own]

Not related to silver but here's a fusion of sonic tails and knuckles : r/silverthehedgehog

Super Sonic + Super Silver Fusion Mask Products from grunty art

SONIC fusion TAILS fusion KNUCKLES fusion SUPER SONIC fusion

Combining 5 Sonic Characters Into 1! (sonic, Tails, Shadow, Knuckles, Silver)