The repops were available through the Chrysler 300 club:

"Reproduction Chrysler 300 air cleaners again available. Both round and acsmall oval styles to fit 58 thru 64 dual 4 bbl cars. Cleaners are steel as original and painted correct colors with correct decals, ready to bolt on. $675 per pair. Call Mike Burke at 517 869 2651 or email: C300F@hotmail.com (08/21/14)"