No-mold Bath Toys
Bath toys can get a bit moldy and gross after a while as they are wet all the time. To avoid this, seal the hole in the toy when you first buy them, with some hot glue which will prevent water from going inside the toy, avoiding mold.
Band-Aids
If you are on a tight schedule and it’s difficult to find the time to get to the hardware store to buy plug protectors, you can use band-aids to seal the plugs as a temporary replacement. Obviously, these are not as fool-proof as plug protectors, depending on how old/nimble with their fingers they are already, so keep an eye still!