there is stuff out there not necassarily sold by ACE but it is called "handi foam" you can prob pick it up at home depot etc. although ace does carry a foam sealant called "beckett foam sealant" but that is used for koi ponds and outdoor waterfalls. the only thing i cant really help you with is the ingredients. your best bet would be to go to the local stores around your area and read the ingredients and see if it is toxic. most of the time it they arent toxic to humans then they arent toxic to animals since our society tests chemicals on animals anyhow. just be careful bc with wear and tear of the foam may cause it to "flake" off and may cuase problems to your pet in the long run.
i may be wrong........but that is just my knowledge of what sealants i have used and seen.