I looked into making one of these years ago. I scaled pics, made drawings and searched day and night for those pesky LEDs. Nothing.
Occasionally a board member would find a handful of them. Very rare.
So I came up with a plan to make them from scratch. I never implemented the idea, but here it is.
Get some plain LED diodes without the acrylic housing. Make a mold of the shape you need and cast them in clear resin using dyes to color them. You can cast clear resin in layers, pouring just enough for a 'top' layer, let it set, then put your leds in the mold and pour the rest. In theory it should set and you won't see a seam line.
It's a major pain in the butt and that's the main reason I never tried it. I put the project on the back burner, hoping I would eventually come across enough LEDs to build one of these. So far, no luck.
Patrick