What technologies/devices will be much harder to find in the future?

Cesium Beam Atomic Clocks - They can keep time accurate to a second in 10,000 years, but the tubes themselves only last 5-7 years of service. Typically they draw on the order of 100 watts.

Obsoleted by

Cesium Vapor Cell Atomic Clocks have a sealed cell of cesium vapor, are probed with a semiconductor laser modulated with microwaves, and draw 1/8 watt in a tiny package, and should last essentially forever.

It can be hard to find an automotive shop with a working OBD1 interface and emissions setup. Luckily that's no longer an issue in some places.

Certain replacement fluorescent ballasts are already hard to find, and that will only accelerate as LEDs replace other fixtures.

Computer-designed flat and microantennas with interesting geometry seem capable of replacing much bigger antennas. Maybe the shape of TV antennas for sale shows that's already complete in consumer electronics.

> P.S.: What is the go-to reference for human technology?

You should repost that paragraph as its own ask HN. That would be a fascinating set of references.

On the desk of a mechanical or chemical engineer I once saw a book containing common or basic machines.

Gasoline, and gasoline powered machinery of any kind.

Benzene is a component of gasoline, and it is a very nasty carcinogen.

General Purpose Offline Computing - Almost everything has to phone home for security updates at some point.

Cars with manual transmission.

Mercury vapor turbines.