So I was thinking of replacing my old and kinda beat up LT-1 aluminum valve covers, and I cannot find any with the push in oil cap that was on a '72.  They all have the twist on metal oil filler cap.
Is there an insert that converts these to the rubber push in oil filler cap?

Unless you want to retain the factory original patina/ oxidation look, you could always have them polished. I had mine polished and they look almost like they're chrome-plated. Course you still have to maintain that surface as aluminum is a moderately active metal. Just requires polishing periodically with a good aluminum polish.

It's not just the finish.  They are chipped and part of one fin is broken off.  

Very interesting Gary !! I was not aware that 72 LT1’s had a push in cap, My ‘73 L82 has it’s original finned covers with the spin on cap. I always thought they were a direct carry-over from the LT1.

You might check with a place that repairs bent, dented, and/or broken aluminum wheels to see if they could fix the broken fin and the dents.

The thing is, it looks like there is an insert, kinda like the crossed flags emblem, that covers the hole with the two slots and converts it to the push in hole. 
I'll have to take a pic to show you.