Looking at parts diagrams it appears the frames for older Thunder 90 & Vipers are a close match. Are he mounting arms for the plastics located in the same place? It looks like the plastics for these things are cheap $. . Is there any other websites with Eton parts? Thoanks.

 

Eton went broke in about 2012 https://alpha-sports.com/eton_parts.htm specialise in pre 2012 parts. A Chinese maker bought the name, but do not make the same machines, so parts for these later bikes are no good for earlier Etons.