Go to Bacons
online and you'll get the theoretical sail plan -- and any used sails they may have that may fit. But I recommend that you take a long piece of line and measure the maximum luff and foot of your particular boat. If you buy a new main from a local sailmaker, he'll measure your boat for you, taking into consideration a number of factors that may need consideration (bimini clearance, backstay/topping list clearance, etc). You;ll also be able to discuss your particular needs with him, like cloth weight and type, batten types, reefing needs, etc. Unless you are really budget stressed, having a new main made for your boat would be my strong preference.