where to buy decent quality tap inserts-

[Pete Williams]

quality product wanted, my 1/4 turn kitchen sink tap inserts need replacing and i am looking for ones with a spindle gland nut, rather than a circlip which previous experiance says won't last five minutes. as the circlip either weakens or wears out.
none of the ironmongery supermarkets appear to stock the type i want.
where can i buy them?