Cat have them if you can't find any good used ones, I bought 8 new liners for my two D4400 engines in the past 18 months from my Cat Dealer here in Australia, price was around $140 each, part number is 7B4348, plus they need 2 rubber O rings 7B2124 and 1 "gasket" under the liner lip 2A3520, do a part search using the Machinery Trader website, it shows the liners available at numerous sources in the USA including FP Smith, American Crane and Florin Tractor Parts.
Mike
I check tomorrow or monday but I should still have 2 or 3 liners 7b4348
I di't found the liners 7b4348 but I recheck tomorrow
I recheck today and have 2 liners 7b43