Quick question…

My Lappiere AM327 has a QR thru Bolt on the rear wheel, its a Formula XQR 12 LA. Whilst riding the nut that secures the far end has become loose and disconnected. Consequently i have lost it.

Any ideas how i can replace it? I have emailed both Formula and the bike shop it came from for advice. Just wondered though, will the bolt be specific to the QR model or will i be able to find a nut elsewhere? Perhaps i will even have to buy another QR unit?

Any ideas? Cheers WW