Blackpol Pleasure Beach Co. sold theirs when they changed their attractions around. About 18-20 years ago.
There are lots of hulls available on the market, all can be fitted with any superstructure wanted to get the "on the water" appearance. Obviously, a hobby grade model hull is likely to cost rather more than a beaten-up toy. A lot of years ago, I recall seeing an "Action Man" boat in a toy shop which was fairly large and looked a bit like a PBR. Don't know if they are still available, but it did look like a candidate for motorising.