I'm sorry no one here has been able to help you. I don't know of any sellers in the EU, but here in the US, Logee's ships internationally. It's quite expensive, though.

I would try contacting the Swedish Botanical Society and ask them if there is a Begonia Society that is active in your country. Here in the US many people participate in the American Begonia Society and they have regional shows. One I think is coming to Miami soon. You can then get choice begonias at the shows and link up with other people interested in begonias. With all the restrictions about shipping between countries due to pests and diseases this seems like the best idea to pursue instead of paying high shipping fees.

Or you may try the National Begonia Society based in England may be they could help you:

http://www.national-begonia-society.co.uk/

Here is a link that might be useful: Swedish Botanical Society

thy these
stbegonias.com
dibleys.com
hodnik.com