I made mine out of 3mm stainless. It's not hard to make a hook providing that you are capable of cutting, bending and drilling 3mm stainless.

The tricky bit is to get the hook dimensions and positioning on the mast just right so that the sail hooks on first go, and then also unhooks easily. I spent a lot of time considering all of that, then ended up fluking a perfect hook for 1434's mast (our other two masts already had hooks).

In designing my hook I took measurements from the other two hooks but the end result was more good fortune than good management. You've gotta be to be lucky sometimes...