years ago I bought a whole box of "shapie" type pens for my darkroom students. They where of archival quality , problem, got them from Light Impressions. These days i wouldn't send the worse person in the world to purchase anything from them. However, perhapes google would turn up something.
We never used these on prints that were to be mounted, sold, etc. basically for easy note keeping.
Be careful about some grease pencil as they may leave a reminder they have been used on the drying screen, just waiting for another print to come by and attach itself ( happened).
Also, sometimes these type of pens bleed through to the print.