The moveset is:
•Knock Off/Any move with the same effect
I was thinking that you could give your opponent pickup, knock off their item, fling an Iron Ball at them, steal it, and repeat. Knock off isn't necessary, just preferable.
You should use the Moveset Searcher tool here on the site for this kind of thing.
Searching for Thief, Fling, and Knock-off produces only 1 result with access to Pickup -- Galarian Zigzagoon. But if you add either Skill Swap or Entrainment, you lose Galarian Zigzagoon. You do, however, keep Ralts, but the challenge then would be getting Pickup onto the Ralts (or more likely, Gallade) in order to make the strategy "go".