The cheapest I found was an Enware one from Benton’s plumbing supplies which cost me $150 posted to Perth. Other prices I found were mostly over $400.
I made my own with a shower curtain and some elastic and use that with a normal bucket. It works really well.
I have made a very primitive sort of setup for this that works for me. I just got a shower curtain from K Mart, a large bucket from Bunnings and a old trolley that nobody likes using and that what I use. Firstly I sewed the sides of the curtain closed so it formed a sock. I threaded an occy strap trough the curtain eyelets – this I use to fir the curtain sock around the head of the shower and I put the trolley with the bucket under the end opening. Very primitive but it works. I also use this curtain sock when flushing the eye station to prevent water from flying all over the place but it just drains through the eye station drain so no need for the bucket there. I bought a little pump online with which I pump the water out of the bucket – either into watering cans for the garden or just to drain it in the sink. I also use the water for making distilled water.
I just get a teacher to hold a bucket up to the shower nozzle while I pull the lever (or vice versa) When the bucket is half full we turn off the lever and empty the bucket.