I'd stick with glass. My 40 year old fixed windows are safety
glass and are finally getting the point of being nice to R&R. It they were plexigalss, would probably have been on their 4th replacement because of UV damage.
Every port manufacturer built there's differantly. They assembled so there is a way to disassemble them hopefully without a larger hammer. If there is such a thing, a marine
glass shop would be the place to get the job done. They'd have some experience with replacing glass in a variety of different ports
. I know it's been done before as a dockmate had his done. Unfortunately that was a long time ago in another state so can't help you with a source.