Hi, this model has a not 3d printed part, the prism, but i guarantee its a very easy thing to do. First cut an acrylic 2mm width in a rectangular shape (80x120mm). Then mark it with a cutter with a separation of 40mm each line like in the image

then fold it in a triangular shape

Seal it with transparent silicone. You can help yourself with a tape.

seal everything together but before you do it you will have to fill it with water. If you dont, nothing is going to make the rainbow. See if there is no leaking and have fun! You just have to put it on the suport and put it under the light of the sun!