Google "marine heat exchangers" and take your pick. Can you easily phone some of the companies from where you are?
One buddy mounted an after market unit off the engine and another got a kit to mount one on the engine.
Also, that seems very young for a heat exchanger to be un fixable. I took my 30 year old unit (3QM30) to a good radiator shop and for $170 they restored it, including cleaning, machining the sealing surfaces and painting the outside.