im sure there is a way, but it would need good knowledge
im not sure if theres any tutorial for this in the internet, and if anything goes wrong your xim might be broken
for the moment it might be easier to look for a new xim2 and sell your current one to someone that doesnt need a mic (with a low price)
or go with a cheap xim1 and save up for a xim3
using the official wireless microphone is the only alternative i can think of but as you said this somehow doesnt work