Shops that sell sewing accessories

I'm looking for a shop in Munich that sells a good selection of sewing accessories. Any recommendations?

In particular I need fabric (that looks like a tape), which is used when one wants to hem pants. Don't really know how it is called neither in English nor German .

Try Karstadt

Herti at the Hauptbahnhof or Ludwig Becks have a large notions department,

Do you mean Saumband? Like Vilene Wundaweb? The iron-on hemming tape?
Hertie haberdashery at HBF, Ludwig Beck Geknopft & Zugenäht, Kaufhof...

I think that's what he means. It's for heming a new set of pants as part of a suit.

YAY - what do I win? He'd still be wise to put a few stiches in too as the stuff isn't always terribly stable depending on the weight of fabric. Handy thing to have on stand-by in any case.

On Thursday November 2nd, Aldi will have some sewing sets for sale.
Looks fine to me...and not expensive