Hi Rob,
this is a very difficult thing to ask, that’s why you have no replies since the 10/01. But saying that, I do specialise in static period ships so may, repeat may be able to assist.
You don’t mention which mast requires the repair, though you do say its the shrouds from deck to crosstrees so they are for the lower mast, but there were 4 masts on her then.
Firstly I would require some accurate photos of your model as is, incorporating at least one measuring stick (ruler), preferably two at right angles to each other, within the area the rigging is required. I would then require photos of the sound rigging that still exists, or of the broken shrouds again alongside so as to try and gauge size.
With these I could possibly judge what is needed for the restoration. Once I’ve made that estimation an attempt at a solution might be forthcoming.
Ideally having the model to hand is the best, and maybe the only solution. I live on the Isle of man so that is probably a non starter.
If you can send those pictures through, we’ll see. I’ll look through my books for the period and trace the vessel.
Kimosubby