Need a temporary greywater tank to get tags from DMV

[Wezeralus]

So my partner and I just finished getting our inspection and enhanced inspection work completed for our skoolie. We were just now informed that in order to get tags from the DMV (Pennsylvania), we still need to have a shower with greywater tank. We have a trip coming up in a few weeks and we need to drive our bus.
Does anyone have information on how to quickly set up a passable-looking, temporary greywater tank? We don’t even need it to be functional at the moment, we just need it to be passable to the DMV for our trip. We will worry about doing it properly after we’ve returned home. We will not be using the shower at all on our trip.

PS-we do have a few rain-collection barrels at home. Let me know if any of them (pictured) could be usable for this purpose.

[john61ct]

Often required for remote camping on public land as well.

I'd install under floor and keep there

but actually plumb to store clean water, maybe valves to switch over if the ranger / inspector wanted to test working.

[PNW_Steve]

I am curious as to where the waste water from the sink in the picture drains to?

Having a working grey tank could prove useful.