Door waterproofing

[Grant]

So with my stripped interior I have removed the door cards and the grey foam behind them. Bad idea. Turns out the grey foam is to stop water splashing off the window regulator and into the car when it rains.

I am reluctant to spend £30 a side for two sheets of foam from pug. What can people reccomend? I don't think I can bang a sheet of plastic or carbon over as I still have the window regulators and they sit proud.

All suggestions welcome. Ta