Hi Kerilli, thanks so much for replying! Yes, I too found the 6" version, but it's too big, I really do need a 5 3/4. Who are NS that you refer to?
Thanks again.
Nothing fancy - all I need is a 5 3/4" magic bit (sometimes called a Cambridge Snaffle), straight mouthpiece with a port and loose rings at the sides. Problem is no-one makes them that big, they're mostly available comercially as 5 1/2", or else the loose rings are too small. So far on Google...