Simple and quick printing replacement spindle lock button for the Dewalt 600 series router, mine is an older DW618PK, but should work for others in the series. 

The small tab that keeps the original button in place broke off which seems to be a common issue as replacements are sold on Amazon and elsewhere for > $10. 

Requires a M5x20mm cap screw and tap. Hole is sized for tapping, you may be able to self tap with the screw if you drill it out to something closer to, but a bit short of M5. A M5x.8 tap is your best bet though.

The M5x20 bolt replaces the pin portion of the original as it is the same diameter and length once fully screwed into the printed part. The lip that prevents the button from coming out of it's hole is set up to print correctly without supports and otherwise the print shouldn't be sensitive to print settings. I would recommend PETG as the router can get a bit warm when running under load for extended periods.

You'll need to remove or at least loosen the 3 screws that hold the cast ring housing down to insert the new part. Once they're tightened back down you should be good to go.