Here is a link that might help.
Wire Rope | IWRC
Not the only place to get this stuff but they do have a good selection and their prices seem reasonable.
Here is another one:
http://www.certifiedslings.com/catalog/
I have been to their retail store in Tampa, FL. If they don't have it, you probably don't need it.
An important note is that when your shopping for snatch blocks you need to match the pulley size with your rope size. Then check to make sure the assembly is rated for the load you intend to put on it. A pulley to small or to large for your rope is not good and will cause problems. Obviously an assembly not rated for your load is a disaster waiting to happen.
Keep in mind that wire rope and snatch blocks are not exactly lightweight. (I have a double pulley assembly for the 45k pound winch on the wrecker, it takes 2 people to move it more than a couple feet.) Shipping charges are likely to be rather significant. You may want to research local suppliers for these items. Check the phone book for wire rope and call some of the local towing companies and ask them where they get their cables and where they get them repaired. Your in Norman, OK and there is a fair amount of oil field work in that area. There are likely 2 or 3 good local places to get everything you need.
Don't forget a few clevises, chokers, chains, nylon straps.. all rated for your intended use of course. You'll find these "Accessories" to be most useful when you start trying to attach cables to various loads and snatch blocks for changing directions and so forth.