I used a large plastic bussing tray - the kind of bin that is used to schlep used crockery back to the kitchen in a restaurant for washing. I bought it at a restaurant supply house - it was a lot less expensive than a similarly-sized plastic bin from an ordinary department store.
I made the inlet using CPVC plastic water pipe - the rigid plastic material that is certified for supply-side use in some jurisdictions in the US. I had some pipe left over from a bathroom construction project, and simply bought some fittings (and ''glue' used to solvent-weld the material. I constructed a pipe rectangle that fit against the wall of the plastic bin with an inlet fitting at the top. Drilled small holes in the pipe at intervals along the rectangle at irregular angles so that the water flow would be more random.
The inlet array was attached to the side of the bin using pipe clamps attached with self-tapping screws. As noted below, I planned to use my washer in a sink, so I wasn't concerned about incidental spillage.
The other issue is how the water exits the washer. The key point there is how it will be used - I had the advantage of a large, deep laundry sink outside the darkroom so all I had to do was drill an array of holes in the side of the bin opposite to the side where I attached my rectangular inlet array. Of course, if you plan to use the washer on a counter top, you need to provide some kind of siphon arrangement rather than just spill greywater over the side.
