As a traveler in Denmark, where should I exchange money to get a relatively good exchange rate?

I’ve had a difficult time in banks to change money. Plenty of bureau de change around, however, be advised, changing something small like $/Euros/GBP 50, or 100, or even 200 might have a high fees. Preferred amount is usually $300 (or equivalent) and higher. In such a case, you will not be paying the 6% or 8% and sometimes even 12% fees.