I am currently on the same schedule you are. Replacing all outside fittings, and resealing windows
etc. Currently on the roof vent...
Where I have had the most success in parts, sealant etc.. is Trotac Marine (Victoria). They have been very helpful. If you're not close by, I would suggest a Marine store.... as it seems their parts seem to be quite well built.
Hope that helps...
I hope to have my 1300 Trillium
all put back together for at least a couple weeks of camping on Lake Cowichan.