After doing a search on here and doing some research on the Internet I have found out that the rear brake pads for the eton viper 90 are as follows,

Moose brand sintered M312-S47 $34.00 denniskirk.com
EBC brand sintered FA83R $20.99 www.rockymountainatv.com or denniskirk.com or ronnies.com
Tusk brand sintered TA83R $14.99 www.Rockymountainatv.com
Factory from dealer 610143 $24.99 Dealer dont know if sintered

These pads are also used on a Suzuki RM 80 year 90-95 front and rear.

I will be ordering the tusk brand to see how they work out and if they fit right. Anybody already using these one these pads now?