Jim. You've got a problem. But so do I, we both like boats. Anyway, you didn't say exactly what saildrive you have, so I hope I'm not wasting my time with assuming you have the O.M.C. saildrive, which was marketed as a Zephyr. Sounds fast, huh? Oh well. It's actually nothing more than that years Johnson/Evinrude 25 H.P. engine, and it's actually been de-tuned for some ungodly reason. Poor idea. Along with that underwater impeller I guess you're now familiar with. So anyhow, the onliest difference in the outboard and the saildrive is the adapter plate that seals it up around the neck of the motor. To keep the boat from sinking, stuff like that. And the lower unit is the same as the outboards as well. Soooooo, with that info, knowing kinda what it is, you may have better luck finding it for the outboard than saildrive/Zephyr.
Nuther thing, Google a boat named Implied Consent. The guys website has a load of info and download PDF's about this saildrive, but it's in an Oday 28. Regardless..