For anyone with older battery powered tools like drills, flashlights, circular saw, Sawzall, etc- I have owned two Milwaukee 18V NiCd hammer drills since about 2005 and at the time, LiIon hadn't quite reached the market. The batteries were expensive, but I got a lot of use from them. The last time I bought Milwaukee replacements, I almost swallowed my tongue and in the time since I got them, Milwaukee stopped supporting NiCd completely, so I looked online because they still work well and I didn't want to replace them because of the cost. I found a couple of dealers on Ebay who sell NiCd replacement battery cells than load into the original plastic shell and they're much more reasonable- I don't think I paid more than $40 for each set. They send a postage paid shipping label for returning the old ones, for recycling and possibly so they can re-use the terminals.
Gulf Coast Battery Company is the one I use.