I'm sorry to hear about your battery issue. Rest assured, Chord will try to assist you in obtaining a replacement battery.
As others have already remarked, it is unwise to try a generic cell with Mojo, as the original cell was developed specifically for Mojo. Not to say that it would be
impossible to use a generic cell, but better to protect your Mojo investment by just using the cell carefully designed to suit Mojo best. Might save a few tears, in the longrun.
With regard to Chord not yet responding, try PM-ing Matt here:
https://www.head-fi.org/conversations/add?to=Matt+Bartlett
...and although it's not an excuse, I should add that a
mitigating circumstance is that the Chord HQ team have a lot on their respective plates at the moment, what with preparing for the
Munich High-End 2018 show.
Perhaps your message may be in someone's e-mail inbox, whilst they are distracted with show preparations?
Whatever the case, if you get no PM response from Matt, and no e-mail response, please don't fret - just PM me and I'll try to assist you.