what are peppadew peppers and if unavailable what is a good substitute??

The peppadew does have a unique flavor. if you try to substutute with a pickled italian pepper you may need to disolve some sugar in the brine. They are usually on par with a sweet pickeled gerkin on the sweetness chart.
you will occasionally find yellow ones as well and they can be substututed for the red.
good luck!

Peppadew peppers are usually available in the grocery story around olive bars. That is less expensive than buying them in jars. You will love them.

These are small (think of a golf ball), globular peppers which are tart and mildly hot. Great for stuffing with cheese or another contrasting flavor. Pickled Italian red peppers are about the closest substitute I can think of.