Low Self Discharge NiMH batteries are your best bet.
They're normally marked as "Pre Charged" or something similar.
Sanyo Eneloop
Maha Imedion
Duracell
AmazonBasics
But, do NOT get EBL brand (sold by Amazon and others)
I bought a bunch of them and they didn't live up to the Low Self Discharge claim.
I could charge them and within a month, they'd all be down to 70%
And I'll second the comment about charging outside of the scanner.
The Nitecore D4 charger is low priced ($25 on eBay) and does a good job.
It will charge 1-4 batteries in any combination of battery sizes and types.
In addition it will charge most other battery chemistries including Li-ION so you'll be all set for anything that comes along.
Rich