I rarely use my Plasplugs indoors, as it still fires out quite a bit of water.
One option though would be to get a galvanised tray, or even a plastic tray for the bottom of dog cages (you can buy them from Welcome to Barjo — Barjo - Dog Guards, Cages and Accessories I can't find them on the website, but if you phone them they definitely sell them. The also make Galv trays to order but aren't cheap), drill a hole in one corner, and place on bath panel with a bucket underneath.
One option though would be to get a galvanised tray, or even a plastic tray for the bottom of dog cages (you can buy them from Welcome to Barjo — Barjo - Dog Guards, Cages and Accessories I can't find them on the website, but if you phone them they definitely sell them. The also make Galv trays to order but aren't cheap), drill a hole in one corner, and place on bath panel with a bucket underneath.