How to get an interference pattern at home?

Question

Physics

I want to show the child an interference pattern at home.
There are a couple of powerful lasers (200 mW and 500 mW, with different wavelengths, green and red light).
But I just can’t figure out how to make or where to buy the grate itself.
Do not tell me how to set up the experiment correctly so that it is as clear as possible? Ideally, it is also better to make a grate at home with your own hands.

Answer 1

Laser printer and transparent heat-resistant film.

Answer 2

Laser pointer and CD-disk
But for reflection, not for transmission...

Answer 3

With interference it's a bit complicated, but with diffraction it's easy, but also impressive. Clamp two straight, straight blades facing each other in a vise, inserting a piece of paper between them. I took two chisels as blades, diffraction was excellent with a conventional laser tape measure.