I picked them up off of Amazon; they're not the best quality but they work for my needs.
Rollbacks use them to winch cars up onto them, hooks right up to the lower control arm or around the axle. I never knew about these until I did a stint driving tow trucks; they are extremely useful.
I've got two sets, one with a longer chain that I keep in my truck.
Mytee Products 5/16"x3' Leg Grade 70 V-Chain Bridle Tow w/ 15" Large Shank J Hook, T-J Hook & Grab Hooks for Towing - 4700 LBS WLL Tow Truck Chain Accessories for Flatbed Trailer Wrecker Recovery: Amazon.com: Industrial & Scientific
www.amazon.com
If I were using them commercially, towing for example, I'd go with a better brand- but for use around the house these work well.