If anyone uses Makita cordless tools, they do a very good 18V compressor. They also do a 12V version but it is somewhat underpowered by all accounts. If you have 18V tools and have the batteries and charger then the compressor is well worth the investment. I used to use a "portable" mains compressor/tank, charge it up with air and do the tyres round the car, but the cordless tool is way more convenient and works so well I rarely use the other, usually only when fitting new tyres and needing the quick rush to get the beads to seat.
If you don't have 18V Makita tools then nothing to see here, move along please!
https://makitauk.com/product/dmp180z(as others say, tyre pressures going down as the weather gets colder is perfectly normal, if they all go down similar amounts, a few psi, then nothing to worry about).