Ran across this earlier when researching the 15-22 firing pin. Perhaps the factory spec'd firing pin spring, extractor spring, etc can be sourced from these guys albeit in bulk length to be cut to spec length.

"Reduced tension stainless steel firing pin spring for S&W M&P 15-22 with reduced pull drop-in triggers. Eliminated light strikes when using 3-3.5lb triggers.
Spring is cut to length of standard firing pin spring.

Purchased long length from McMaster-Carr, part number 966K13, 302 stainless steel Cut-to-Length Compression Spring, .187" OD, .17" wire diameter."

For accuracy and fairness, here's the raw link: ARMSLIST - For Sale: Firing Pin Spring for S&W M&P 15-22

I dont know if I like stepping down in thickness that far just saying....