Tweede Kamer, Dampkring, Bushdocter. Not cheap, nothing is in the centre of Amsterdam, but with the ones above you'll at least get what you pay for. If you have time to take a trip to the Belgian border, Maastricht (2.5 hrs from Amsterdam by car) is a lot cheaper but busy as hell on the weekends with Belgians, French and Germans all stocking up for the week to come.

Enjoy your trip.

Edit - and don't forget to visit Sensi's Hash, Marijuana and Hemp Museum :thumbsup: