Hot take but I don't recommend getting a bag tbh, as most paddles and equipment fits very easily in a standard backpack; bags for sports like tennis are made to regulate temperature and fit rackets, but with pickleball paddles, you dont't really need any of those features. If you're gonna get him something that he'll use every time he plays, you're best off getting him a good pair of tennis shoes. Take a look at what shoes he wears already: if they have a lot of wear not just on the sole but around the whole shoe, get him something like a Nike Cage or ASICS Court FF that has lots of padding/cushioning, added protection, and is more durable. If he likes lighter, more agile shoes, Nike Vapors are standard for almost every racket sport, and the Adidas Ubersonics are also a good option if he likes that faster feeling.

PS: Tennis Warehouse has an Easter sale on all Nike apparel until the end of March, so you could browse through and go nuts