Not sure if I recommend this. I had all the parts within reach at the time so it was a natural. 1/4 npt tap. 1/4 x 1/8 npt brass reducer bushing. 1/8 npt plug.
Tapped bushing into hole and tightened with red Loctite. 1/8 plug is plenty big to drain the tiny amount of fluid when needed.
Helicoil is the proper way to do this. For me the brass fittings were a simpler option.