You might also want the coil brackets, the shift linkage for the transmission, the spacers for the rear fork (we call it a swinger in the US) and make sure you get the double u-joint for drive shaft.
I also used the exhaust clamps from the stock bike. If you are using a rear wheel from the bike you will need that too. If you are getting the 15" wheel for the car type tire there are a few items from the cush drive on the moto wheel that needs to transfer over. You would also need the rear axle.
Make sure the engine has the stator coil and rotor as well as the regulator / rectifier. Rear shocks can also be used and the hardware that goes with it, although I hear there is a little Swedish company that is rumored to make some pretty good shocks.
Like many have said it is much much easier to get a complete bike and sell the rest. You are sure to find a few items that you need from the bike that were missed above and other posts.
Can you find a complete donor bike in NL and take that back to Sweden? You don't need to be able to ride the bike. Its nice just to have a complete bike for all the parts you need.
Good luck with the build. It was like Legos for big kids. So much fun.
When I bought my Triking it was already ordered and shipped to Johann of Triking USA. It was already spec'd out with certain options so I had no chance to add or delete options. It came with ox blood red leather interior. I was originally going to go with vinyl interior to save a little money. So glad I got the leather. It really is nice. It also has the pleated tunnel cover and the little pockets in the side panels, both upgrades. I think it really makes it look better. The reverse gear option is well worth it too. Touring windshield a plus over the two individual screens.
Ivan