The panel on your Axis is identical to my 28Z (except for the blank covers over the tank heater switches on my panel ).
I bought the one on eBay assuming the monitor uses the same technology. It has the same resistor ladder network cable and well nuts, and is made by the same company.
The foil sensor looks like this:
I got a good price on them $20. But they are normally $35. I don't know if they charged me $20 just because of being a repeat customer, or if they are interested in my idea of using their sensors for the monitor. I figured for $20, it was not worth trying to come up with my own.