You could have a foundry design & cast you a custom gypsy, but by the time they were done, you'd likely have spent less by simply purchasing
a different windlass.
Though if you query enough foundaries in seafaring towns, you might get lucky. Here's one, for a start Port Townsend Foundry in Washington
Also, can you not modify your current
chain locker to be a bit bigger? It might take a few days of glass work
, after you do the cutting, but...
It's either that, or stow more chain elsewhere. Which leads me to the next option...
- When you get close to the end of what's in your locker, chain wise, attach another 40m (or whatever) to your current
chain through a pre-positioned shackle on/in your daily use rode.
You can do this by using a heavy duty snap link (locking, screw gate, stainless or titanium carabiner), or, better yet. A Crosby high load shackle (the varient with a threaded pin with nut, & a hole for a safety
wire or ring pin in the end).
That way, you're only dealing with the extra chain when you really need it. And it can reside elsewhere, aside from the primary chain locker. The same trick can be done to add some rope to your primary rode as well.
To pull in a combination rode without a gypsy designed for both. Attach a 2ndary line to the rope part of your rode, with a rolling hitch, up near the cross beam. And then lead that line to a snatch block on the boat's stern quarter, & from there, to a primary winch in your cockpit
. Preferably a powered one.
Then, about the time that that 1st rolling hitch gets back to the snatch block, your partner puts a 2nd line onto the rope rode, up at the crossbeam, & back to a snatch block on the boat's other side, & forward to a big winch.
Repeat until you get to where your windlass can well grab the chain.
So, given that your boat's 50' long, it shouldn't take too many repetitions of this manuever to get to where you're back to hauling up your chain & hook the usual way.
Also, if your budget
can take it. Often enough, if you throw a wrap or two of rope rode fully around a gypsy desned only for chain, it will haul in a rope rode. But the price
is accelerated wear from chafe.
Or as Robert Heinlein often said, TANSTAAFL - There Ain't No Such Thing As A Free Lunch.
PS: Before doing any cutting of the structure which comprises your chain locker. If it's part of any cross beams, or significan parts
of the boat's structure, talk to the maker first. As cutting the wrong thing could be bad for obvious reasons.