You should be able to cut the probes off twist the wires together put some heat transfer paste inside the thermowell. Put the wire inside the thermowell and hold it in place with a strain relief that screws into the thermowell.
I have the 30L model, the handles after I looked at them were easy to put on lol. I was thinking the same about the gallon marker, start at the seem and go from there. Thanks for the reply.