City idsi is quite a comfortable car. Finding a replacement in this budget is quite difficult, especially one that would be anywhere near as economical as that. I would suggest to wait a while till you can afford a better car, in the given amount, nothing like an idsi.
Vitz in original 1.3 are very difficult to source, most are converts and those are not worth it.
You can try looking for a 2006 se saloon auto but that isn't as comfortable nor as economical as your car. If auto is your only concern, try sourcing a mint steermatic, that might be as near to a good replacement as your car in the given budget