Ok I feel like these could work:

Daniel Kahn and the Painted Bird:

• Arbeitlosemarsch (Mix of English and Yiddish)

Mischief Brew:

• Preacher and the Slave
• Every Town Will Celebrate Someday

These are more IWW style songs but they're still fairly upbeat

Pete Seeger:

• If I had a Hammer
• Solidarity Forever
• Down by the Riverside (Study War No More)

Faith Petric:

• Ain't Done Nothing if You Ain't Been Called a Red

Billy Bragg:

• Union Maid (The original version is a bit sexist by modern standards)