Not only are there many different risers available, but also different LED stripes, and it can be difficult to find something suitable.
I have created this diffusor is for the LED Riser Modular by Benjamin Kott - MakerWorld, since this is one of the best risers out there.
Because not all LED's transmit the light the same way, there are 2 different versions available, “Thick Wall” and “Thin Wall”, so you can find the best option for your LED stripe.
The material used in the pictures is the Bambu Lab PETG clear translucent and the thick wall model version.
My recommendation is to print the “test pieces” plate first to find the best looking version for your LED stripe. Once you have the right version, simply delete the unwanted plates and objects.
The assembly is pretty straight forward. The longer parts are for the longer side of the riser, the shorter parts for the shorter. The easiest way to install the diffusor is to insert the corner first, as shown in the GIF picture. In case you have glued your riser, it may require a bit more patience during the installation. :)
A short disclaimer:
I am by no means an experienced 3D printer user, and you may want to optimize the print profile further. Furthermore, you may want to smooth the corners with file a tiny bit so they match perfectly.