A vagabond 14 was my first boat! They are fun to sail and quite rugged and stable.
Mine bent a few times and I just bent it back. There shouldn't be much load on that part except for when you are raising and lowering the mast so you should be OK.
If you can't find the part, try finding who made the mast and contact them directly. I have a Vanguard Nomad and I had to do that myself as by the time I got my boat the Laser folks had taken over and they didn't know anything about the Vanguard boats and they were exceptionally and extremely rude. I had one even threaten to contact my boss because I had used a work e-mail to contact them.
Final idea would be to go to a local machine shop, and it shouldn't cost too much to have one fabricated. Actually my main boat is a Compac 27 and the Compac folks do stainless fabrication for other builders in FL, so they might be able to help you.