If you insist on decaf, choose only that using the Swiss Water Process.
I would be very interested in your reasons for decaf. If it is health related, you may have cause to question the medical professional and what information their opinion is based on.
Unless you are one of the extreme minority with a very low tolerance for caffeine, coffee offers a multitude of health benefits, such as more antioxidants than blueberries.
As for a good source of beans, check for local roasters in your area. A good Colombian Supremo Swiss Water Decaf would be a good start. This is a readilly available bean in just about any roaster or independent coffee shops offering.
If you have a flat or conical burr grinder you're way ahead of the game. If you have a blade or whirlly grinder you may want to have the roaster or coffee shop grind it for you. In that case you will absolutely need a really good air tight container to store it in to maintain freshness as long as possible.
Believe it or not, the grind makes a big difference in the flavor of the coffee. If you're willing to put out $100 or so, you can get a decent conical burr grinder. Solis makes a good choice. But $200+ for a Technivorum brewer might be a little extreme at this stage.
But soon, you may be like the rest of us extremists, with the $2000 fully automatics, $400 grinders, $720 roasters, with autographed Illy cups drinking Yemen Mocha! Aaahhh...what a life!