Towing eye replacement

Would anyone be able to tell me the actual thread size of the front towing eye, as well as somewhere I could buy a bolt the same size from?
I am planning on fitting a tow strap as boost pipes make it impossible to fit the original towing eye.
I would like to use a bolt to hold the strap in place nice and firmly should the day come I require a tow.
I have been to a screws/bolts/fastener sort of place however they were unable to help me. Apparently they didn't stock that size... Internet searches have also proved to be fruitless.
I was told the thread needed was "18mm with a 2.5mm pitch" and obviously left handed. That makes it an M16 size bolt, is that correct?

My other option should the 'shop bought' bolt method prove to be too much hassle is to saw the thread off the towing eye, cut a big cross in it and screw it in place. Either that or weld a bolt head onto the towing eye thread.
I have seen pictures of people drilling through the towing eye slot and fixing a bolt through the hole, secured with a nut on the other end. I'd rather not start drilling holes in the car just yet.

Any suggestions / advice is much appreciated.

JRJG