Rich Pierce flints are really good sparkers, but the white color can be off-putting to some... but not me! Hard to think the HC rondy police would object, as white flint has been around in MS and KS for a billion years. The amber French flints have also worked well for me, generally available from ToTW & Dixie.
You can re-do the edge of a flint with a green wheel (used for sharpening carbide tools) IF you can figure out how to hold the old flint against the grinding wheel. I use vise-grips & leather wrapper.
I have a dismal success rate at re-knapping flints. After I re-knap one, their either don't work at all, or work once or twice.
Green wheels for your bench grinder are not cheap, but widely available at Graingers, WS Mars, ENCO, etc. Green wheel good for shortening the flint, as some Pedersoli locks need a short flint to allow the frizzen to fully close on the pan.