If you don't want to order the neon flexible tubing from AliExpress or you simply want an alternative right now rather than waiting for it to ship, you can print this. It should just fit into the slot. Affix the LED strip to either the inside or outside side (your preference) of the diffuser. Otherwise assemble as normal. NOTE: You may have to modify the chain_count value in your printer.cfg to match the correct number of LEDs used.
The author remixed this model.