I had a quote from Ian Porter recently as follows:
“We have all the necessary fittings in stock –
The protex over-throw lever and catch works out at £13.35inc VAT each.
The turnbutton and striker plates are £4.90 inc VAT each.
So as one requires two pairs of each assembly the cost would be £36.50 inc VAT plus carriage.”
Hope this helps – works fine on my boat.