I need help finding a pulley for my stepper motor, from 5mm diameter shaft to 1/4" screw
just like this one:
where can i find it?
Your description isn't very clear. The picture shows a timing pulley and if you want that duplicated you will need the tooth pitch and how many teeth. Your best bet is going to be: http://www.sdp-si.com. They have an app that even calculates belt length given pulley parameters and distance. Good Luck.
Here's another source.
They're a good company.