I guess its a question of whether he is a genuine diligent seller, in which case he should be willing to complete the transaction once you have assured him you're happy with the gloves "as is". Or, whether he just didn't like the price they sold at...have you tried diplomatically suggesting you're more likely to neg him for not providing the gloves? If he refuses to send them, I don't think there's anything you can do except neg him (in which case, he'll probably neg you back
)
Sometimes its best just to walk away from an ebay deal that's turning bad (particularly as you haven't lost any money). If he's dodgy, he'll probably be more than ready to neg you spuriously if you give him a hard time.