main drain leak

[quacka]

i have a leak in the main drain area, but it actually a crack in the sump portion...you know, that coffee can shaped part that feeds the main drain line and the VGB cover attached to. Anyway, I filled the cracks with A/B Epoxy last year and that has worked until now. I was thinking, since I have two (2) skimmers, I don't need the main drain as I've read that here, but I need a way to cover the main drain sump to prevent leaking. I've seen the vinyl covers you can put over the VGB covers to create more suction for a robot or vacuum, but I'm looking for something more lasting - such as a solid, water tight main drain cover. Does such a beast exist? If not, any ideas how to fix without cutting out sump?