Are you dueling with this mount or is a twin (dual) mount?
The mount should also fit the M249 and I have no idea of pricing. There aren't a lot of M240's out there in civvie hands so probably not a huge demand. You might check Ohio Ordnance Works site as they have been the distributors for these mounts for some time....they have the can mounts and pintle though.
I talked to Ohio Ord and they make them. I asked if they would be interested in maybe getting it back and they said nope. Also thank you for the dual correction I didn't even notice lol. I may have more luck on gunbroker.