Anyone hoping to be an extraordinary housefly for Halloween this year after tuning into the VP debate is s*** outta luck ... because the costume is sold out!!!

Sorry, seems lots of folks already decided to be the infamous housefly that landed on Mike Pence's head during the debate ... honchos at HalloweenCostumes.com tell us their "adult fly costume" is out of stock and their supplier is sold out too.

The Halloween costume retailer tells us they carried a normal amount of stock for this particular costume -- about 50 -- but they saw a huge demand right after the debate, causing the costume to fly off the shelf.

If you wanna settle for a housefly costume that's just headgear, you're gonna have to wait ... the site tells us their other fly costume is also sold out -- all 150 in stock were snatched up after the debate -- but they hope to get it back in stock by Friday.

Seems the only people who don't want to be a debate housefly are those too young to vote ... you can still find a fly costume for toddlers.