Realistically, I am pretty sure I can make my own custom toilet-flush frame for my MA certificate.
There are unnecessarily complicated birthday cards which have a little battery-powered recorder gizzy so you can record your own greeting.
When I could do is disembowel one of those cards, record a toilet flush sound effect on the recorder gizzy using a REAL TOILET and then conceal that on the back of the frame.
The flushing sound effect would be activated by a pull-cord, I think. It would be the most thematically faithful.
And this way, I can just use any old cheap secondhand frame I can find at a thrift shop, providing I can find one that will accommodate A4 paper. Seeing as we don’t deal much in A4 here in the USA, therein lies my challenge.