I bought one of the Cosmos holograms, which I believe is the hard part, and since I used to do 3D CAD modeling for Apple and Next, I believe it will be quite easy to replicate the bezel to create a replica. (Even though I have a Makerbot, I'd rather use an SLA printer and mold/cast to make quality realistic parts.)
The LED array and double 7-segment display seems simple enough to replicate without any special hardware. (Perhaps I can find a generic calculator of the era that has the segmented numbers for the score display.) Ideally a replica will contain an emulated COPS411 processor just to make the historical aspects of the device slightly more authentic. What I (think) I know:
512 bytes ROM acting as eight pages of 64 bytes each - hence eight built in games?
128 bits of ram
IO using a 4-bit shift register
Does anyone have any information on how the games played? Do any manuals exist? There was a Cosmos sold on ebay about five years ago, that apparently had pictures of it disassembled, is there any chance someone here has archived those?
Archive.org, Google, & wikipedia so far are dead-ends, with only the already generally known information, most of the results are verbatim copies of Wikipedia's entry, though a few sites also claim the AdventureVison by Entex used the same processor, which seems to be incorrect.