Effect Unit
From Amazon
Fender 2-Button Footswitch - Channel Select and Effects On/Off
The product is available from £29.92 at international stores.
GAK
Fender Footswitch, 2 Button, FM65DSP/Super-Champ XD, 1/4 Connector
guitar.co.uk
Fender 2-Button Footswitch for Super Champ and Champion