Mobiky is heavy last I tried one.

You might do better with a-bike.co.uk (US$300), which is useless for anything but short rides on smooth surfaces. You can buy knockoff a-bikes on ebay as low as $75 with shipping, that probably are functional but almost certainly have cheaper drivetrain components and no support/returns. If you like the knockoff go for the $300 original.

Small differences in weight make a big difference if you are carrying it while carring other things, and rushing from train to train.

Brompton, Strida, and Birdy while expensive can double as a general purpose bike.

Another possibility is just buy a cheap bike and a chain it near the station and leave it.