Simple, a mini foot pump with tyre pressure gauge.
Weighing just 450 grams and at 20 cm long by 8 cm across and high, you can slip this in a cycle saddle bag or unclutter a boot.
Yet, amazingly still pump up quickly.
Air pressure readings are shown on the tyre pressure gauge as in psi (pounds per square inch) and in kg per square cm.
Then it is foot and eye operated.
No complexity, you already know how to use these!
These are mini, smaller than normal foot pumps so you can carry the pump with you on your bike.
Sturdy metal construction, enamel paint construction, bits to inflate gym balls and much else as well as tyres.