Do you have a link to the bulbs that you went with Martin?
this is the link to the eBay item I bought, which is in the German site:
http://www.ebay.de/itm/221481001420And I also found them for you guys in Amazon.com, but they cost a bit more over there:
http://www.amazon.com/Philips-Blue-Vision-Ultra-Pair/dp/B001B4TJVA/ref=sr_1_1?s=automotive&ie=UTF8&qid=1414756998&sr=1-1&keywords=Philips+3400kIn Amazon Germany they also cost about 6€ (8 USD).
I should mention that my interest was twofold: increase the light output and get white lights. The H4 X-trem Vision that I got accomplish both without being bluish, which I don't like. These city lights should match the headlights now...
@Jim: thanks. At work I don't have the manual at hand, but I have something else... the bike
So I went out and had a look and it looks like you're right and once you get the 4 rivets out, the little bulbs should be easily reachable.