Paul
For one off projects that should be no big problem.
Shipping would be higher.
I'm from the EU (aka outside the US) and then things get even worse. Shipping and customs handling are a substantial part. And then I'm not talking about...
I've used miniLZO in the past (not on teensy), but it uses GPL.
LZ4 is another more recent one (BSD license if i'm correct). LZ4 is used with ZFS.
Edit: For production LZ4 would be my favorite, but miniLZO is maybe easier to start?
As I have almost no soldering skills :
A small "low height" board with at least 1 or 2 qwiic connectors and quite a few pins on different jst connectors. Adding a circuit so that we can program a keep powerbank alive cycle would be nice (mosfet...