I know a lot of players use Smith Optics Boogie Regulator goggles, which can be purchased with an optional bungee kit which attaches to the swivel mounts often supplied with FAST/MICH helmets. However, I have seen reviews which suggest they are prone to fogging. Other than that, it's probably as Lozart suggests where you can shorten or mod the goggle straps to clip into the swivel mounts. On my goggles this will mean cutting the straps as there is not a way of unbuckling them.
However, there is a downside of attaching goggles to helmet which is that the eyepro has to be removed if you want to take your helmet off. Whilst this shouldn't be a big problem in most skirmish/CQB games, if you play games with long game times, or games where you will be out of any safe zone for long periods, or milsim-type experiences which require you to keep eyepro in place at all times you will be wearing your helmet for looooong periods which can be very uncomfortable. And, if you ever do a overnight milsim, you may need to sleep in your helmet. Ouch.