You can deffinitely buy them off eBay, and hope they are good quality, and that you won't have to replace them a month later.
Or, you can spend a few more dollars (unless your time installing the possibly inferior parts is not worth anything to you), and get some Moog control arms from places like five Star Ford, rock auto, etc.
On a side note, even RA has been known to sell the wrong stuff. I ordered a set of bushings for my 98's Ps rack, and they were totally the wrong design. I called them up, and the guy on the phone was adamant about them being the right bushings. Needless to say, Maxx found a set in some warehouse in timbuktu nowhere.