So you need a new gooseneck bracket, eh? Well, time to employ some Google-foo.
As others stated, Beneteau uses
Z-Spar components. The Beneteau First 24 in particular has a mast section labelled Z230 and uses the Z160 gooseneck assembly on the boom, as you can see from the hyperlinked page. You are in luck! Z-Spar is still in business.
You might want to try someone like
Rig-Rite for consultation and part ordering. They stock a lot of replacements for old hardware. I have never used them personally so I can't say how their service or knowledge is, but their
selection of older gooseneck brackets looks promising. Just eye-balling it, I'd say your broken piece is a Z-1478C, which is compatible with the Z230 mast section. But don't depend on me to decide. Measure the broken piece then call them to ensure you know the right piece before you order.
I agree with the others, the gooseneck casting you have now does not look like it fits the bracket. So while you are at it, measure your gooseneck casting and talk to them about it. I think it should be a
Z-160-1, but consult the parts experts to be sure.
And and get yourself a proper pin that fits the hole! This is likely why the casting broke in the first place. A carriage bolt that is smaller than the hole concentrates the force on a line rather than spreading it across the entire tab. To continue using a carriage bolt is just begging for trouble.
Also, feel free to work with some other company instead Rig-Rite. I only used Rig-Rite because they were at the top of the Google list and I can find stuff on their site.
Final update: While reading the later entries on this thread, I saw afrinus recommends US Spars. I'm sure they are a fine company and would serve you well. However, if you order part 3355 you are going to get the gooseneck, not the gooseneck bracket. According to
their break-out, the bracket is part number 4063, is called the Gooseneck Base, and
lists for 24.73. My opinion about the gooseneck casting and pin also apply here. Once again, I recommend measuring and calling before ordering to ensure you get the right pieces. this may be especially important in your case. I see other holes in your picture and suspect I am not looking at original equipment.