I did one of these as a proof of concept for storing gpg keys long term, securely and offline.
My version didn't use a motor and required a human to pull the tape through, had a set of guide holes down the middle to indicate when a bit was to be read and used LEDs as both the light sources and the photo receptors.
All in all a rather fun project which worked much better than it had any right to.
Never did find a material which had the longevity of aluminium foil with the durability of 35mm film stock.
A friend had a commercial paper tape reader (don't recall who made it) from the S-100/8080/CP-M homebrew era built exactly like that. It was the 'inexpensive' version (they had motorized versions), and was finicky but worked OK for small amounts of code. CP/M actually has a built-in papertape reader device in bios called RDR: (tho it was often repurposed for other kinds of devices).
For something as short as a gpg key, you can easily use stamped brass “tape” 0.1-3mm in thickness. You can roll it like tape if it’s thin enough or just store it as a bar if your pattern is dense enough.
(Also note that OP’s version doesn’t require a motor either and can be actuated by hand, per TFA.)
My version didn't use a motor and required a human to pull the tape through, had a set of guide holes down the middle to indicate when a bit was to be read and used LEDs as both the light sources and the photo receptors.
All in all a rather fun project which worked much better than it had any right to.
Never did find a material which had the longevity of aluminium foil with the durability of 35mm film stock.