Seized oil filler cap

I recently bought a 2019 yz250f off an individual. Damn near every bolt this guy touched has been gorilla sealed. Usually has taken several days/penetrating fluids/other people to sit on the wrench to try to get it to budge. very frustrating. the oil filler cap is a size 8 Allen wrench that I haven't gotten to budge for 3 days of working on it. It's also stripped to hell. plyers aren't working. I've gone through a ton of penetrating fluids. warming it up hasn't helped. I need a way of getting this stupid cap off so I can go ride. any advice would be greatly appreciated!