In regards to a recent request for a battery replacement on a Waterpik model sr3000w in particular, we have located a handy little do-it-yourself video concerning the battery pack replacement for the Waterpik using an alternate battery pack.
In addition, here is a video that shows the process in more detail, although its a different model its still the same type of battery pack and concept. YouTube
They use a rechargeable battery pack that consists of 2 AAA batteries rated at 1.2V 800maH, the P213-F021-ND in our catalog is rated for 700maH so will not last quite as long as the original but in the terms of price and convenience, this is a great alternate option HHR70AAAB8F2 Panasonic - BSG | Battery Products | DigiKey
A set of helping hands like this is also a good tool addition when dealing with trying to hold the component along with desoldering it. 2197-JA-40-ND https://www.digikey.com/short/zfd31n