For wired headphones there are headphone splitters but for bluetooth I think you need a Bluetooth adapter.
There are some in form of PCIE cards, which provide WiFi and/or Bluetooth, however, you want to use them on a laptop so they're not compatible with your use case.
Some are small USB dongles and depending on model allow more than one device to be paired/connected. The USB dongle ones are usually around $15-20. Like this one
here.
Some are bigger than dongles and are like USB flash drives, some have external antennas too. Some of these just have a broadcast mode and just allow audio transmission to headphones or headsets which is basically what you want I guess. Like this one
here.
Apparently some of there are only compatible with Windows and not other OSs, probably manufacturer just a makes drivers for Windows.
I don't personally know of a good quality model and have seen users complain that some of these adapters fail after a short while, or connections drop and so on. You can wait and see if other users here have any experience with these or actually know of good models.