said by garys_2k:
Plumber's putty? A foam back rod and GE II caulk on that?
How often do you think you'll need to open it? Will you just wait until it doesn't work, monthly, semi-annual or annual inspections?
I think that something like this may be your best bet »www.dynamicrubber.com/inflatable···dex.html but I don't know where you'd pick one up.
Maybe maybe... all ideas are valid
The rubber thing seems a bit hard to find as you said, but the principle is similar to the rubber seal at the bottom of garage doors (another idea).
As for the frequency: I'm guessing it would be a semi-annual inspection. It's the first time I deal with a sump pump. The pit was originally filled with gravel by the previous owners for what look like DECADES so that pit will probably not see much action (yay dry land!).