First you need to get an equivalent charger and some type of male/female or contact harness. This will have to have at least three pins as that is what is already on the Dremel. Now the difficult decision, do you want to open up the Dremel if it's still under warranty? If you don't mind opening it then my solution will work. Open up the Dremel and look at the inside of the contacts. As this is a DC charger it can only have positive and negative terminals. You say there are three contacts, so there will either be two positive and one negative or two negative and one positive. Most likely there will be a bridge wire between the two terminals with the same polarity. Strip a little of the insulation from the terminal wires and solder new leads to your contact harness. Noting the polarity of each pin/contact on the new harness wire the other part of the contact harness to the charger. You will most likely have to make a small hole in the Dremel's outer cover to allow the wires to pass through. As you own a Dremel I'm sure you are capable of attempting this easy bit of DIY. There is only one problem, If the third contact plate is a return signal to the charging base it might be to inform the charger when the battery is full. In this case the terminals inside the Dremel will not be bridged and I suggest you buy a new or secondhand charger. Hope this helps