First, grays and piney squirrels are not anyway near the tenacity, toughness, sinewy, 9 lives, etc, of a Fox squirrel, period!
Tough as a wild tom cat!
For a cheap and efficient, diy point, here's what works for me.
I take my old, used field points, be the 125 or more in grain weight. Blunt the tip with either a file or grinder, flat! Then clamp in vice on an old shaft, or use 2 vice grips, one to hold the shaft, point, and the other to hold that vicegrip to a solid flat surface.
Then hacksaw a slot, about a 1/2" deep. Now you need some banding steel 1" wide, like found at a lumber yard, factory,machine shop or scrap yard. Even ole replacement style modular brodheads could be used.
Cut a piece of the banding about 3/4" long, using shears, chisel, or dremel. Either in a triangle shape or half moon. Now insert in slot, align by your eye, and super glue!
When dry and ready, take a file and sharpen up the leading edge, doesn't have to be razor, just sharp!
I use these on my Acme Ramin shafts, and chundoo or heavy pine. Along with broadheads for ground shots, this is my arsenal for Squirrels!