I'd forgotten all about TaburYak dinghies. About 30 years ago, my first boat was moored on a quiet river in Suffolk, on the far bank from the boatyard, and several TaburYak dinghies were available at the boatyard for people to row across to their boats.
As I recall, the TaburYak dinghies were rotationally moulded from polyethylene (or similar). Repairing fairly simple damage involves melting some similar plastic in to the "wound", using some sort of heat gun or soldering iron. Larger damage is very difficult to repair. If you just have simple damage, you could try repairing it yourself. Makers of rotationally moulded items like navigation buoys often offer repair kits (see www.tidelandsignal.com/mp-buoys.pdf as an example). Or, as an alternative, talk to your local automotive bodyshops and ask who they'd recommend for heat-welding a plastic bumper.