The charger, if you find it, is almost guaranteed to cost more than a new drill. Actually, chargers for anything often cost more than the product, whether it's a cordless tool, a cell phone, or a shaver. It has to do with the law of supply and demand - because companies sell way more kits that include everything, including a charger, than they do of just the chargers, they manufacture a lot more of them. Retailers make more on the kits than they would if they could stock all of the thousands of different chargers types that are made every year.
If your drill is more than a few years old, the battery or batteries are probably getting ready to die, anyway. It's just the nature of the beast and even professional quality tool batteries eventually stop accepting a charge, no matter how much they are used. Extreme heat and cold speed up the process, so you shouldn't leave your batteries in a trunk or unheated garage if you live where there is severe weather. Because your battery contains the heavy metal, Cadmium, it should be properly disposed of an not tossed in a landfill because it can leach into the groundwater supply. By the way, Panasonic makes all the batteries for Black & Decker/DeWalt, among others, though that may change now that they are owned by the Stanley Corporation. I'm sorry to be the bearer of bad news, but I wouldn't recommend spending a lot more time looking for this charger unless your drill is less than a year old. It might even be cheaper to buy a new kit if you can find one that comes with a charger that your batteries will fit. I know it sounds weird, but I did the same thing when I was on a business trip and had grabbed my son's cell phone charger by mistake. I had to buy a different phone because it came with a charger that would work on mine and it was cheaper than the charger by itself. It's the same with power tools, unfortunately.
Cabinetmaker and carpenter for over 20 years. Black & Decker trained tool repairman. The tool industry is going through a lot of consolidation and there is a tremendous amount of pressure to find the next generation of battery technology for everything from communication devices to automobiles.