HP 67 programming?

[Thomas Okken]

They have become more expensive in recent years, but even at $300-400, you're paying a fraction of the original price. They were $450 in 1976, that's equivalent to $2000 today.

N.B. If you do go shopping around for one, make sure to budget an additional $100 or so to get the card reader fixed, those almost invariably need to be repaired because the rubber on the pinch roller turns to goo over time. Sometimes you'll see one offered that has already had that repair done, but most haven't.