Bringing back weird oddities like calculators or transistors is going to cause questions. Even something which is available but expensive is unlikely to be in the hands of a private individual in significant quantities (e.g. the transistors), so as soon as any questions are asked, you've got no trail as to where they came from, so they'll (at best) look stolen.

The simple answer is to forge old cash. The forging technology available now would exceed the detection capability in 1968.

Bringing back weird oddities like calculators or transistors is going to cause questions. Even something which is available but expensive is unlikely to be in the hands of a private individual in significant quantities (e.g. the transistors), so as soon as any questions are asked, you've got no trail as to where they came from, so they'll (at best) look stolen.

The simple answer is to forge old cash. The forging technology available now would exceed the detection capability in 1968, and whilst (depending on your jurisdiction) forging out-of-circulation currency may still be a crime, if you’re caught it’s probably much easier to explain as a “historical project” or for re-enactment etc. Crucially though the materials needed to forge out-of-date currency are probably not controlled any more, so you won’t get on any watch-lists buying them.