Brake Push Rod Boot

Hi All,

I am reusing my old push rod on a new master cylinder. I found a replacement rubber "keeper"...the rubber gasket that holds the push rod inside the master cylinder.

I cannot however locate a source for the rubber boot to firewall piece. Mine was of course chewed to oblivion. Does anyone know where to find this boot?

I found this one on Mancini Racing's website but there is no photo or much of a description so I'm not sure if it is what i need. Manual Brake Master Cylinder Boot for Plunger Rod

Is there an adequate substitution out there - maybe from a newer vehicle?

1974 Swinger 225ci with Manual Brakes, Disc Front/Drum Rear.

Thanks!