Try this number with Dave in JBL Pro Parts. Its a 8/32 x 1.5 long Filister head, Black Torx drive, not the same as original but if the head is the right size, may be a decent sub.
803-02010-24 SCR,8-32 X 1 1/2,FIL,TORX,BLK ZINC,LCS $ 0 .42 USD EA
I couldn't find a pdf for the 2420 showing engineering drawings or part numbers.
Otherwise, contact Smith fasteners above and maybe request a sample?
Regards,
Bart