Looking at all the various options your best chances may be just renting a car for the duration of your trip.... there used to be a direct flights with easyjet but that's gone :-( Trains are going to be long and expensive... It's a bit of drive but can be easliy done in a day. All train trips seem to take at least 24hrs..... 

Thanks. Martin. Yes, I have a car to drive. Could be an option. May be even cheaper.

We are looking for a crew member. May be we will find one who could join me for the drive.

Thanks again

Jing

You are welcome, went 3 -4 times by car to Istria, works absolutely fine... Just don't forget the Slovenian Autoroute vignette - which now can be ordered online :-) 

Thank you for the info about Vignette. Now I am checking all countries I will drve through this year.