I'm sure golf smith or Maltby's sell the paint fill.  If not a good enamel paint will do the trick.  Just make sure you clean the irons well and use alcohol prior and let dry and then have at it.  I would remove the remaining black you still have before repainting.

I'm very sorry for the late response. I check out this site every single waking second of the day. It's my second home. I must have accidentally skipped over it.

I use nail polish. I can't think of the brand, but...if I need to paint...I'll clean the club(s) spotless, make sure they're very dry, then paint a coat...let it sit a few hours, then paint another coat and let it sit over night.

If you need some help, etc., feel free to get a hold of me.