Most commercial electronic stores will have them.
Home Depot might even have them. They carry Lutron stuff for the home.
Depending on how much room you have, if possible, don't mount the block directly to the wallboard. Put a 2X2 foot (or 4X4 foot) 3/4" ply-wood backing board up, then attach all your stuff to that.
Also, while there are a number of patch blocks available, you might ultimately be better off (hanging on your backing baord) a wall-mount panel rack. They're usually only about 8-10" deep, and have room for 2-10 rack spaces (size varies). Using a wall-mount rack will give you some room to grow in case you want to add, for example, a panel of "F" connectors for your TV/cableTV/Satellite signal distribution, or, another panel of video jacks....
Either way, putting up a backingboard will save your walls, and gives you someplace to screw-down cable management stuff, or other small accessories.
FWIW
Scott