The likes of South Korea, India, Singapore and Thailand all rule them out since they have been Israeli customers for a while and have (relative) transparency regarding these deals.
Taiwan would have been too politically hot for Israel to handle since the Chinese would have known very early.
An educated guess would be either Vietnam or Indonesia. Both are trying to diversify away from Russian systems but don’t have the clout to purchase everything they want from the West. So Israel is a reasonable bet. A couple of years ago, there were reports that Israel was planning to sell/had sold UAVs to Indonesia.