From the image you posted, you should have little trouble finding such an item, or, having one made. As that kind of design is very common.
And, that said. Your gooseneck, especially the part which connects/fits onto the mast, needn't be made of stainless, by any means. And, in fact, a very large percentage of them are made of aluminum
Which is a lot easier to work, work with, & to bend to shape. As it can be formed & shaped, etc., pretty much using only woodworking tools.
Also, since it's lower in strength than is stainless, the fitting will be bigger, in terms of connective area. And that's a good thing, as it helps to spread the loads out over a larger area of the mast. Which is aluminum
as well. Ergo, you'll have less issues with point loading, & with dissimilar metal corrosion
Really, if you wanted to, the whole thing could be made entirely of aluminum. Though in reality, it's common for; the hinge pin, any hooks or high load fittings, plus the attachment screws that connect it to the mast tube, to be made of stainless. While isolating the 2 metals from one another as much as possible.
If you do a simple Google
or Bing image search for "sailboat goosenecks", & or "sailboat vangs" (where the vangs attach to the mast), you'll turn up all kinds of examples of what I'm saying.
And also, there are some images
of such, plus lots off advice on the topic, in the Dashew's Offshore Cruising Encyclopedia Vol.II
Which you can download for free, at www.setsail.com
Also, if you spend a bit of time talking to riggers, odds are they'll have a few used goosenecks, in need of a home laying around. Ditto on boatyards
Though you may have to pull them off of the masts yourself, & perhaps buy the booms as well (for cheap). And the boom may actually be an upgrade, having more useful features than your current
Or, it may be a fairly simple matter to remove (or cut) the gooseneck off of it, & attach it to your current
boom (possibly requiring the services of a welder).
One other option, to aide in getting a custom one made. Is to get some door skins, or 1/4" plywood
, & a hot glue gun, plus some 5-minute epoxy
. And use it to make a mock up of what you're after.
- Make the first set of patterns (for the wood) out of cardboard.
And for the metal bits, just use some aluminum rod, & bits of coat hanger wire. Along with some fishing
line, or 1/8" line, to seize the bits together, in position. Again, using epoxy, or epoxy putty, if you want to get fancy, or a bit more structural, in terms of connecting them.
But any fabricator will be more than satisfied if you use coathanger for the mockup's hinge pins, & other custom metal bits. If the rest of your DIY, wooden gooseneck is reasonably well put together.
Plus, take pictures & sketches with you, along with some dimensional drawings to the fabricator/rigger. Preferably ones of the mechanical/technical type.
As they should cover most of what's needed, in terms of; specifications, angles, & material thicknesses, needed in order to make your (ideal) custom gooseneck.
Though the "finished" gooseneck may require a bit of bending; possibly involving a hammer & or vise, in order to get it to fit perfectly. But that's quite common, & no big deal.
BTW, this also applies if you happen to snag a used unit, from another vessel. Via a rig shop, used gear chandlery
Once you have your new 9or pre-loved) gooseneck. All you'll need to do, is to drill the holes for the attachment screws, & bond/bolt the unit into place.
Ah, & there's plenty of info on bonding Aluminum (& other metals) on the WEST System site, & in the downloadable books
& publications there.
Though, strictly speaking, bonding your gooseneck to the mast, isn't truly a requirement, if it's well fastened, with numerous, tapped, machine screws. Though, them I'd bond (& simultaneously isolate) with Blue