Since the original front cover for the oscilloscope is quite pricey, I designed and printed one myself. To save material, I just designed a frame to hold a 5mm thickness plate of a light but sturdy material, e.g. hard foam material or even clear plastic material. To allow for 3D-Printing on normal printers, the frame consists of two halves that can be screwed together. 
Tip: I 2D-Printed a 1:1 photo of the oscilloscope and glued it to the plate, so the oscilloscope looks less boring when the cover is in use.

I printed it using PETG, but PLA should work as well.