A number of effect pedal makers (the ones that come to mind now are Death By Audio and JPTR FX from Germany) have business cards that are actual, usable PCBs.
If you have one, from them or any other pedal maker, I want it! Probably — reach out and let me know what you got, and I'll let you know if I'm interested.
Also willing to consider usable PCB business cards from other industries (if such a thing exists).
Will pay a reasonable price (comparable to commercially available DIY boards, $3-5 or so, depending). Can cover reasonable shipping.