PinRestore has material and have used it several times now with good results. You’ll may want a punch hole cutter and Dremel tool too.
https://www.pinrestore.com/Supplies.html
“Spring Steel for Ramp Flaps
3" wide blue spring steel for cutting out new ramp flaps, .007" thick. Also useful for cutting out replacement springs for flipper opto interrupters. Sold in 1 foot lengths. This cuts easily with ordinary scissors or tin snips.
$8.00 per foot”