clamber1122 - do you have a 3D printer? If you do then I'm surprised you don't know the names of the materials used - the manual usually tells you the name and they usually have a customer service line that you can call. If you don't - they are really expensive ($200-500 for a low end model) that seems to be an excessively expensive way to solve your problem. I have a 3D drawing pen that I've used to make a part for my black glasses - it really worked - I just held the glasses in one hand and the pen in the other and attached the two plastics, then since this was a really small piece, melted plastic to the other end of the piece I was making - I made it slope just like the original did and it held the lens of the glasses in place.
. The pen could easily make a rather flat piece like you're describing in just about any size you need, It's called "the doodler" - look on Amazon, I think right now they cost about $80, They just call the materials "plastic" - one is PLA the other is ACL or something like that, PLA heats hotter than the ACL but you select which kind you are using and the pen heats it to the proper temperature, it's easily as hot as hot glue which if you melted some down and made a mold out of aluminum foil then poured the hot glue into the mold it would work just the same, you would have to do some research (probably in a craft's forum to see if it will leech into water). As far as the pen, you could just call the manufacturer and see what they can tell you about the type of plastics they use, You could also take a tupperware container (or the cheaper version at the grocery store) and cut a piece out of it that would be the right size then see if that silicone stuff that they seal aquariums with would "glue" it to the overflow container, You know both the tupperware plastic and the silicone is safe for fish since both are safe for people.
Hopefully I'm at least understanding your question. When I've talked to customer service about their pen and the plastics they always referred to them as plastics not "resins", now with a 3D printer that may be different but I don't know why it would be. Their customer service is really good - I managed to get a new pen out of them even though it was past the warranty time - which is a big problem with this product I went through 3 of them before I got one that worked consistently, If you send me a drawing with measurements on it I could make it for you and send it to you but I wouldn't have anyway to attach it to the overflow
Since supposedly hot glue doesn't degrade in water melting some of that down and pouring it into a mold made out of aluminum foil and then glueing it to the overflow sounds like the best idea, When I first got the doodler pen I thought hot glue could behave the same way,
