Plastic containers for drainpipe wetland (Ware SG12)

Hi there, I’m looking to build a drainpipe wetland similar to the one in the photo. For this I would need some plastic boxes or containers. Maybe even an old baby bath would do. If anyone has one or more they no longer need, I’d be very appreciative. I’m based in Ware so looking to pick up from not too far away. Many thanks.