You can purchase lids for fish tanks in order to convert them into vivs. They come with a ventilation mesh and a socket for a bulb. Saw them in the pet shop today.
depends on what you're doing for a lid JS the mesh ones you can buy are expensive but have good ventilation (as they're mesh!) if it's a home-made lid then we'd need to see a piccy
cornsnakes, ratsnakes, bullsnakes, boas and day geckos Location:Leeds/York/Selby area
although just because it isn't air tight doesn't mean that it will necessarily have enough ventilation to maintain correct humidity. Maybe worth considering.