Not 100% sure of what it would take, but I would think you would need the following components to build a stomp box to do this...
#1. A click on / click off footswitch. SPST most likely.
#2. 1/4" (6.5mm) TS jack.
#3. A properly sized electrical project box / chassis.
#4. "Sufficiently sized" wire, say 16 gauge in red and black or whatever colors you so choose, red and black are the typical for power / ground although other colors can be used, as long as YOU know what is going on...
#5. Crimp on female blade connectors OR NON ACID solder and soldering iron. The latter is the FAR better method.
#6. Electrical tape to manage your wire.
#7. A surface mountable LED to indicate active / inactive for the circuit.
#8. A wiring diagram of what you are trying to accomplish, or not...
#9. A 1/4" (6.5mm) instrument cable to connect switch to amp)
I would think, unless you have those parts in your inventory already, you might be better off money wise just buying the switch.
Doesn't need to be that complicated.
#1 SPST switch
#2 1/4" jack
#3 Box...could be a project box (I used a 1590a), could be an old bean dip can
#4 Pedal wire. Any light gauge electric wire will do (battery snap leads, wire pulled from home electronics).
#5 Regular guitar cable
No wiring diagram needed. Connect one lug on the jack to one lug on the switch; connect the other lug on the jack to the other lug on the switch. Soldering should go without saying, but there's not a lot of current here, so you could just wrap the wire into the lugs and tape it up, I reckon.
LED is interesting, I'm still trying to wrap my head around how the Fender switches work, because it would have to be that the cable is carrying some amount of current to power the light. Otherwise, you could of course put in a DPST switch and a battery to power it locally in the box.
