I don't know if you speak German, but as soon as the Opeth/Katatonia-gig is listed, you might be lucky and order tickets from there. http://www.kartenhaus.de
Until now they only got concerts that take place on November 15th at the latest, yet there are all Logo-gigs listed so I expect them to care for this one, too.
Hope this helps...
www.ticketweb.com, and www.ticketmaster.com may be of help, keep checking nearer the date though also if you see a poster or add in a magazine then it usually says a telephone number or web address next to it, i think there will be one in Terrorizer next month