Need I really say more?
To all those new to the area, every spring and autumn lots of churches in your area run "kinderkleiderbörse"/ flea market, where you can get used seasonal kids/baby clothes and toys very very cheeply. (sometimes babybjörn, beds, whatever)
The best one in my area (in my humble oppinion) is at the St Sebastian Church in Wettingen, on the corner of Rebbergstrasse & Schartenstrasse. Starts at 3pm.. there is a cresh. Dont take a pram into the room!!!! (you can park it outside thou..) Carry the baby in a sling or something.

The number 3 bus would get you there too, direction Brunnenwiese.
http://www.rvbw.ch/rvbw/linienplan.aspx

Suggest you do a "search" on kinderkleiderbörse. Some are advertised on http://www.event-planer.ch/index2.php

You did not mention the date of this Kinderkleiderbörse. Was it the day of the post? or is it still coming up`?

The title of the post gives all the information!