Very low output rating, so just a simple 10 Ah lipo with a voltage converter .
Something like one of their Mulistar 2 C cells probably ?
You could even make 4 of them from this one pack..for ~ $40
https://hobbyking.com/en_us/multistar-high-capacity-4s-10000mah-multi-rotor-lipo-pack.html
I bet that has three 18650 cells inside. Just like the similar devices you see everywhere now days. One cell and two cell ones are in most stores these days. Larger ones a bit harder to find.
?? Why the interest ?
It cannot be a very "special" cell, low output, etc...probably just "c" grade stuff..
And it is not very good value $/Wh ?
Multistar's are much better and cheaper
So unless you need a USB back up,.....why bother ?