Nut for ironing board (Gleneagles area, Wboro NN8)

One of the stainless steel dome nuts holding our ironing board has come off and will not be found.
It looks like the first photo. The measurements are in the next photograph.

I think it may be 8mm (8m) diameter

If anybody within NN8 has one rolling around in a spare bits drawer, I would be very grateful to make use of it. A wing nut or something similar would also work.
Many thanks,
Susan