I have a 2006 Mainship 34. I obtained a replacement engine room air vent assembly from Dick Bramer
Boat Lovers Surplus & Fabrication LLC
603 Cidco Road
Cocoa, Florida 32926
He may have other Mainship parts. It worth a call. I found him by using Trawler Forum searches. I am a satisfied customer, I have no commercial interest in Mr. Bramer's company.