I am just finishing up building a bike with a 1" threadless headset (first bike I've built with a non-threaded headset, so sorry if this is a dumb question!). There's a very small gap between the stem and headset, about 2mm (picture attached). I need a spacer there, right? If so, if anyone has a 2mm spacer for a 1" fork... I'll pay you to mail it to me! And separately, how important is the size - should I overshoot or undershoot? Thanks!

-Colin