http://buy1.snapon.com/catalog/item...roup_ID=682403&store=snapon-store&dir=catalog
Although I unfortunately bought mine before they moved the stupid button to the bottom. And I need the spring-loaded bit than engages the head replaced, it slips if you pull hard. I've yet to find any locking flex that doesn't eventually quit locking. But it's still infinitely more versatile than a fixed ratchet, and not a knuckle-busting troll of a tool like a non-locking one.
I got tired of having that one fixed and bought a Matco:
http://www.matcotools.com/catalog/product/BFR128LFT/3-8-DRIVE-88-TOOTH-LOCKING-FLEX-RATCHET/
...on which the lock broke in about 1/10th the time. Completely. And 88 teeth my fucking ass, it's rougher than Snapon's 60 tooth ratchets.
Even so, it's still better than most. I'll castrate myself before I use a Craftsman ratchet. Those pieces of shit feel like they have about seven gear teeth, and they were hand cut by a retarded toddler with Parkinsons.
edit: oh, and for 1/4" I use a THL936A (...yeah, I had to go look at it). Even at 36 teeth, it's still smoother and resets more quickly than most other 1/4 ratchets. And it's got a bitchin' green handle. And it was free because I found it underneath someone's carpet.