Google the ball brand and model you want. You will find someplace online that sells it. Lately I’ve been buying tennis balls and shoes from all kinds of online stores that I never had to shop at before.
My loyalty to TW has totally gone down the drain as they are always out of stock in the last two years for just about anything I want to buy. Or they say it will be in stock in a month and then ship in three months - the least they can do is stop being so aggressive with their ‘In stock’ dates as I don’t see other stores being so consistently late on quoted ship dates.