You can check the box saying the buyer did not want the item, and mark it as mutualy agreed not to complete, or item unavailable. (This short-circuits the normal seven-day waiting period for filing.)
Then the buyer must respond or get an unpaid item strike and lose the right to leave feedback.
They may clear it by paying again of course, but it's pretty hard to ignore an unpaid item dispute notice.
If they respond you are risking a neg, but you are always in danger of a neg just by dealing on ebay. The worst I got was a neut from an unavailable item, which I though unfair as it was an accidentally duplicated listing of what was clearly the same item
(Used vintage photogrphic equipment rarley comes in matched pairs with identical serial numbers, and this buyer bid on both
)