If you are not relatively close to the vendor of a starter, things can get problematic and expensive. Getting a starter shipped across the Pacific ocean or past slow, laborious customs officers can be very challenging.
If frhd is looking for the components to make cheese and he's not in North America, Europe or Australia, things can be less than easy. I suggest looking at the international list of vendors here, there may be a cheese supply closer than you realize, frhd.
As the other members noted, cultured buttermilk and yogurt can be used for starters as well. Here is a company in the USA that sells a buttermilk culture that is not so temperature sensitive, so it can be shipped overseas:
http://www.culturesforhealth.com/buttermilk-starter-318.html You can check out their yogurt cultures too. They have one that works at room temperature and can be shipped overseas without special packaging (cooling packs). But you already have access to yogurt so that is probably less interesting to you.
Good luck with your yogurt substitution. I hope it works for you. I may try the same thing shortly. I have ordered both the buttermilk and yogurt starters myself.
I saw the comment about making a clabber, something I need to learn about!