NiCds in a Retail shop? Also 800mAH is unlikely for AA NiCd.
I'd avoid those and stick with 1800mAH to 2200mA quality NiMH, just takes longer to fully charge (which would be the case with the dubiously labelled 800mAH NiCd.
Quality NiMH are not a problem.
Many places have decent NiMH cheaply. Avoid less than 1800mAH or more than 2500mAH.
NiCd are available for specialist applications. But not in Retail. There is no point to them for a Scanner. I use regular NiMH in my Radios and Scanners that were from NiCd era with no problem.
The main issue with the high self discharge ones is finding it flat unless you are recharging every few days. I have two sets for more heavily used stuff.
These are panasonic version of the Sanyo Eneloophttp://www.maplin.co.uk/p/panasonic-evo ... pack-n30na
The only limitation is that if orginal NiCd were 300mAH to 500mAH, the charge rate will be about 30mA to 50mA. So don't leave them on charge for more than 70 hours. It may take 25 to 60 hours in the original charger circuit to fully charge due to higher capacity. But as there is little memory effect compared to NiCd, partial use and charge overnight isn't a problem.
About 4 to 5x longer use than NiCd. At low consumption (< 30mA) though, Alkaline still beat them for capacity. Only at > 100mA load is NiMH going to look a lot better.