NiMH is what you want.

NiCads are cheaper but lack capacity, and anything Lithium is relatively expensive by any metric.

@jerv I was hoping for a specific link to buy. I have for instance purchased off ebay.com and found the measured capacity was 1/6th the rated capacity.

Also: I am not sure if Lithium is expensive. LiFePO4 may be the CHEAPEST when you take into account they make packs you can discharge to 70% 4000 times or 80% 2000 times. I use a lot of Lithium-Ion in 18650 format. The voltage is 3.7 instead of 1.2 for NiHM so you get about three times the energy for rated mAh. You can get a 18650 format Lithium -Ion with good specs (probably a LIE) from ebay.com delivered for $3 from China. I like 26650 format the best but there is a lack of devices which can use it. 18650 format gives me a lot more battery life and a lot less time switching batteries. For instance a device which uses three 18650 format batteries would need to use 9 AA NiMH batteries which at some point becomes a pain.