CPL make a whole variety which are correct in detail for their specific purpose. I fit them to all my 0-gauge stuff.
There's also an interesting (if small) range from Exactoscale which actually feature correctly operating turnbuckles! They also have steel links which may appeal to some.
Len Newman of Exactoscale does some good working screw couplings, Standard, GWR & Southern Patterns.
He also lists the long and short D links and draw hooks as seperate items.