I would just go with the screen top and acrylic if needed to retain humidity. The canopies always look nice and kind of give the tank a finished look, but with frogs it is often easier not to go that route. Plus, you want to keep in mind the lighting for the tank. If you are using heat lights it is probably best to leave it open on the top so the heat from the fixture can dissipate easily. Besides, a canopy can always be added later if you really want one. And I'm sure you could find a way to make the canopy rest on the top. I was given a homemade aquarium stand and canopy. The wood for the canopy goes around the outside edge of the glass (encasing it if you will) and there are a couple small wooden blocks screwed in on the inside so the canopy only rests on the plastic frame of the tank (I can send you a picture if that makes the explanation clearer). The other option of having an aquarium lid and replacing the center strip with screen sounds reasonable, but my only concern would be whether or not there would be enough ventilation in the tank. It you're having trouble finding a glass lid from a major retailer your best bet would be a small mom-and-pop aquarium store. They usually have odds and ends like that, or they can at least order them for you.