Pepper is probably okay, but it's hard to tell. As far as time goes, maybe three weeks with no/minimal eating should be cause for concern- but I'm thinking about White's Tree Frogs here and I'm not an expert.

If you end up needing a cheap emergency tank, you can get a large clear plastic storage bin, cut a hole in the top with an x-acto knife, cover the hole with some form of mesh, using hot glue. Let the glue dry and wash down the bin very well with dechlorinated water.