The Crushgrind ceramic grinder mechanism is the best I have come across - it produces an excellent grind reliably. Being made of ceramic, it is capable of grinding salt and pepper (or any other small spice) equally. Indeed, the recommended way to clean the mechanism is to run some coarse salt through it.
These are very easy mechanisms to fit and you do not need to be accurate on length as the top pushes on rather than being held on by a little screw cap. The only slightly tricky part is cutting a rebate for the plastic spring clips to fit in - but a tool can easily be made by grinding up a cheap Chinese chisel. Dimensions and instructions on how to use them can be found on Crushgrind's Austrailian partner's website. That site suggests grinding off the spring tabs, but it is much better to leave them on and cut a rebate - it is not that hard.
I have some surplus 10 inch mechanisms. Details for online ordering to follow; in the main time please use the contact me link..
I'm selling them for £5 each plus postage at cost while stock lasts. You should find that price very hard to beat. Note that these are old stock and of the older design of mechanism.