At no load 13 & a bit V at the battery is a good thing!
I would guess if you managed to remove a terminal on the choke switch your ignition switch won't be too far behind.....
1) a gallon of WD40 into the ign switch, turn it off & on a few dozen times & hope.
2) new switch.
no idea of the cost, it's one of the few things on my rig that haven't died on me so far!
If you are Ok with solderng or crimping, and have the switches on a panel rather than rammed into the remote control, there is an argument that most 2- stroke generation ignition switches would work as long as it had "short on off", switched power & a sprung start position. Most of the modern ones have a "push key in to choke" function, so removing the separate choke switch.
If you want to be a bit creative, what is likely a lower budget option is a simple Maplin key switch (on- off to break ignition - do you even need it with your use?), a DPDT with one side wired "power" the other (opposing) side wired across the deadman (the stop-go selector) and a couple of push buttons / sprung toggles for start & choke. The only dowwn side (as I found on my electrical rebuild) is that the only switches they do vaguely IP rated are the toggles with the rubber covers. Having said that, I bet someone like RS would stock them. (other electrical retailers are avaialble!