Bummer. Sadly, there is no substitute; you'll have to scour the usual sources for second hand kit, since they aren't made anymore.
I'm a huge fan of the Ilford 500 series enlarger heads, and I can tell you that it's a good idea to keep a constant eye out for parts- not that they fail often, but when they do, there isn't much you can do. They don't come up for sale often, but when they do, it's either very cheap or very expensive; it's best to jump on the deals whenever you find them, so that you have parts in as insurance against failure. None of this helps you now, but keep your eyes open. Hopefully you'll be able to source a spare soon. Good luck!