Last summer I did a similar trip. I ended up buying my Topas Stealth in Copenhagen. It was the cheapest of the countries I had visited. Russia will be the most expensive. Actually if I could have found it in Estonia, I think that would have been the cheapest place for me to buy it as their dept stores typically have great sales.
I got the VAT back at the airport. I paid using a Canadian credit card, and our dollar wasn't so strong, but it still wasn't a bad price. After tax back I'd say 1200-1300 Canadian for 82L one, which is pretty good compared to what I would pay in Canada for the same thing.
There are 3 places to buy in Copenhagen. I bought in the department store...where bon gout travel is..yes it is in a department store on the 2nd or 3rd floor. They had the full line of stealth, the others did not.
Just going to let you know Norway is the most expensive country so I wouldn't even waste your time looking there if I were you.
Good luck.
(BTW the reason I bought it wasn't planned, my suitcase was a cheap make that had a zipper all the way around. The zipper got damaged so that once I got it open, it would not close again...therefore I had to buy a suitcase. I figured I'd go with my dream suitcase rather than buying another cheap one)