Brand name is Dicor, same people who make the sealant products, trim is called " Versa Liner " and if it's like mine you have two missing parts, a cap ( push on type) and a threaded retainer.
If you pull straight off with a gloved hand, on the 180 degree opposite cover, you should expose the threaded retainer that will look like this. IF the product is exactly the same as mine.
I have the web site address in another computer , I'll post as soon as I can track it down.
EDIT: Got back in time to add it here