This is a remix of the 1/2 inch bias tape maker that Mquin123 posted. The smaller tape maker had really thin walls, and my machine wouldn't print them. I've thickened the walls and made it slightly different, but all credit goes to Mquin123 - thanks.

ps. I've added the sketchup file, but be warned it's a bit of a mess - I used the Netfabb service to clean up the stl so I could print it.

EDIT - Forgot to say, if you rotate it 90 degrees, it prints upright without any supports.