Companies like Nylet do replacement sails. Fittings are generally very common across lots of different yachts, largely a question of getting the size right. If you have the sails, they are the clue needed as to the lengths of mast and booms. Reading the Nylet price list, the main is shown as having a corded luff, which says to me that it needs a grooved mast.
The Fairwind has been a popular boat, there is an after-market for it.
Talking to your chosen supplier should set you on the right path, they will have run into the problem before.
Otherwise, a trip to Wickes or B&Q, a good look at their metal section section and some imagination, but my memories of the Fairwind say that it was a rather tender boat, so saving as much weight as possible above deck is important. Being popular, it also has threads on other sites, like RCgroups.