Jackdaw's suggestion is on the mark. However, I would look for a manufacturer's decal on the mast to be safe. At that time, due to a long story which I am not going into, several mast manufacturers were used to include US Spars (formerly Z Spar). Charleston Spar (Formely Kenyon Isomat and now Sparcraft) or Dwyer Aluminum.
If there is no manufacture's decal, take a photo of the spreader bar and post it so we can identify. If US Spar, you can go direct or the forum store which will have the exact one and the cost is about the same either way. If Dwyer Aluminum, not sure about the forum store but you can go direct. If Charleston Spar, go to Rigrite and they will get the right part to you but do include the model, Hunter 240.
Hunter set up this site forum store years ago and even the old Hunter is gone, they have the parts for your boat and one member or salesman on staff use to work at Hunter in warranty and of all things, dealer and retail parts. You will find the forum store very helpful, courteous and above board professional.
I use to be a dealer and know the small boats too well..