Get from Amazon.com : http://www.amazon.com/gp/product/B001535826?tag=hawaiianlegac-20

Go Power! GP-TS 30 Amp Prewired Transfer Switch for Quick Connect

Prewired 30 amp automatic transfer switch
Plug and play installation
Made for use with inverter shore power or generators
Extra outlet wired for charger
Delay switch for use with generators