In their comments on my previous post, both Adithi's Amma and Veronique asked for more information about where to buy sewing supplies in Amsterdam. I will email both of them to answer specific questions but I thought I might as well dedicate a post to sharing what little information I have on the subject.
(I will include links to the websites of the various stores, unfortunately, those are only in Dutch. Don't worry though, people working at these stores will speak more than enough English to help you)
As I mentioned before, Kantje Boord is an Alladin's cave for the lingerie seamstress. You can order online, but that may be only within the Netherlands. The store adress is:
Burgemeester van Leeuwenlaan 45-47
1064 KK Amsterdam
It's easy to reach by car and you don't have to pay for parking in the area. Travelling there by public transport may be less than simple though.
A. Boeken is a large store selling notions and fabric and pretty much in the city center. It's latest claim to fame is supplying fabric and notions for the Dutch version of "Project Runway". The adress is:
Nieuwe Hoogstraat 31
1011 HD Amsterdam
For general fabric and habedashery shopping in Amsterdam, I wouldn't recommend a single store. I'd recommend an area which houses many: Take the tram to the Albert Cuyp.
At this location, a general street market including stalls selling fabric is held every day except Sundays and Holidays. More important for us, seamstresses, are the stores lining the street: lots of fabric stores. The best known one is probably Kniphal, it's the largest and I seem to remember it's where Knipmode (a Dutch sewing magazine) gets most of its fabrics. The adress is:
Albert Cuypstraat 162-164
1073 BK Amsterdam
Both A. Boeken and the Albert Cuyp are easy to reach by public transport. I wouldn't recommend taking the car to either destination. It's too busy and parking is expensive.
I hope this is useful to any of you who are going to visit Amsterdam. Since I don't live in that city, I'm pretty sure there are other stores I didn't include. If you have anything to add, please let me know.