You might be able to get a salvage condition 2011/2012 LEAF for cheap (<$2000), drop the battery from it, and then install it in your LEAF but it's certainly not a trivial undertaking. I personally don't think it would be worth the money or effort though, as any salvage 2011/2012 LEAF likely has lost a couple of bars already.
A better option would be a battery pack from a 2013/2014/2015, but that's even more complicated to DIY.
This video gives you an idea of the complexity involved:https://www.youtube.com/watch?v=mBBk1ABKftg
Vancouver, CA owner of a 2013 Ocean Blue SV + QC, purchased 01/2017 in WA
Zencar 12/20/24/30A L1/L2 portable EVSE
1-1/4" Curt #11396 hitch
After market, DIY LED DRLs
LeafSpy Pro + Konnwei KW902 ELM327 BT OBDII dongle
Loving my first BEV