I've never seen them available anywhere commercially.

Two peppers that are somewhat similar (although probably not identical) are Paprika Pepper "Alma" and one from Franchi Seminti Seed(via Seeds of Italy, I think, in the USA) called "Satan's Kiss". I've grown both and they are quite good, but I've never tried Peppadew so can't say how they compare. "Alma" plants are usually available from retailers in mid-Spring.

This was discussed a couple of years back on the pepper forum. I've linked that discussion here for you.

Dawn

Here is a link that might be useful: Pepper Forum Thread on Peppadew