I'm not having much luck searching for tie-rod ends. They are all still 90 degrees.

The closest thing I can see is on the mcmaster.com link: Heavy Duty Inline Ball Joint Linkages. These are almost exactly what I'm after.

It needs to be fairly precise. The ones in the first picture I posted would be suitable if they weren't 90 degrees.
They will only get a few days use each year.
I'm hoping to find a set of 4 ball studs and cups for around £10 but I'll pay more if I need to.

They will be used to move the eyes in one of my Halloween props so they can't be any bigger than the normal ones used with servos. The eyes will give next to no resistance so they don't have to be too strong and won't wear too quick. I do need to be able to pop them apart though which is why I'm not using small Ujoints.