I don't believe the foam boats are manufactured any more. Used ones come up for sale by members of this list, from time to time.
Similar solid boats are made out of plastic by a few manufacturers, without all of the many disadvantages of the styrofoam boat. Here is a link:
https://directboats.com/kickboats.htmlCheck out the Pit Boss and the VO, check around for prices, Walmart used to carry one of them for Less.