I doubt "free sex swinger parties" is a thing. If it's a party, somebody's gonna host it and has to pay for it, so there's an entry fee. Also, no sex is guaranteed on swinger parties, you still have to find a suitable partner to fuck yourself there, and if nobody is interested, bad luck. If you want guaranteed sex, book a sexworker. They don't work for free either, though.
TBH I find it incredibly rude to post here seriously hoping to find somebody to give you sex with no effort. Might be news for you, but: most people aren't desperate enough to just randomly fuck people just because they exist. Especially if apparently fucking isn't worth anything to them.