You can no longer find the Trizone brush heads on the Oral-B homepage, but they are still sold everywhere. You can use all brush heads except the iO series with your appliance. I personally like the Oral-B Cross Action CleanMaximiser and the Oral-B Sensitive Clean brushes best.

Unfortunately I don't know. I just couldn't get the brushes at Migros any more. They always said they were not available at the moment...