shift or throttle

I bought a 1988 E-28 last summer. The knobs were missing for the shift and throttle. (The PO has passed away and his wife held on to the boat for 4 years before deciding to sell it and she had no idea where they went). Anyway the pedestal is a Yacht Specialties and the thread pattern measures...

Check out the photo below. Does anyone know the manufacturer of the engine control shown? I like these because the levers can be removed to minimize line tangles, throttle kicks, trips, etc. Can these still be obtained? Raleigh