Have you posted on the Capri 16.5 Yahoo Group? If not, join it and post there too; someone may have one.
If you don't have any luck there, try Roger at River City Sailing in Portland. I know in the past he's offered to have parts from Catalina sent up when he has a boat or other stuff coming up so little or no additional shipping. Who knows, he might even have a Capri 16.5 in stock.
I love my Capri 22, and wouldn't trade it, but I wish I'd been able to keep the 16.5 too. It's a fun boat.