Arbosil 1081 black or clear to choice.Basically aquarium sealant /adhesive used for making tanks.
It's what is used to fine point replacement hatch perspex perimeter after bedding on butyl strip.
I used it to rebed my cabin windows successfully after several attampts by others using neoprene tape.
Available Hadlow Marine /Construction Sealants etc. , about £8 per tube,plus any postage.
I assume there's a wide perimeter bed so the sealant is going to be more convenient than a narow butyl strip but thats an alternative.