Try:

Devilish Mary
Black Dog and Sheepcrook
I Wonder What's Keeping My True Love Tonight
'Gin I Were a Baron's Heir (not strictly dumping, but ...)
Pretty Saro
'Twas on an April Morning
Young Roger the Miller (mutual, serial dumping)
Rich Irish Lady (she rejects him, dies repenting)
Loving Hannah (aka I Went to Mass Last Sunday)
I Once Loved A Lass (aka The Week Before Easter, The False Bride)
The Nobleman's Wedding

I'm sure there are lots more. Some of these may not be the particular flavor of rejection you are seeking. There's "Barbara Allen," of course.

I don't have the capacity to create MIDI files, but I imagine some of these things might be in the DT.

Good Luck