A modern car should be able to be left for extended periods without a flat battery. You could always consider a trickle charger to keep the battery topped up - something like the CTEK MXS: kit.honestjohn.co.uk/reviews/review-ctek-battery-c.../. If you don't have access to electricity where you park your car, you could look at a solar-powered trickle charger - this can be left on your dashboard and uses the sun to keep your battery topped up.

A Hyundai i10 is a great little car and ought to be reliable. But an EV would be ideal for your requirements - the main battery will provide power to the 12V battery, so it's less likely to leave you stranded if unused for a longer period. We'd recommend a Fiat 500 Electric or Peugeot e-208.