Is the center steering arm bent..?? If it's a little loose on the steering shaft, I have removed them, and ground a bit off the inside where it's split, so as to snug up on the shaft. If it's bent, or beyond repair, then a good used replacement may be all you find. I do remember seeing new ones several years back in aftermarket parts books, but can't seem to come up with one now.
Here is a link to Bates IH.
Products :: 356554R1U Center Steering Arm, Round, A/B They have new & used parts. The link will take you to a picture of a used steering arm they have. It says they have 19 of them in their inventory. Be setting down when you open it up, LOL..
Another option, is to go here to TractorHouse:
http://www.tractorhouse.com/list/dismantledsearch.aspx?ETID=3&Manu=INTERNATIONAL&Mdltxt=A&mdlx=exact I've already selected the list of 19 Farmall A's in salvage yards. 5 have pictures, so as to have a look at the tie rods, and see if they are pretty much straight. I don't know that the price will be much different from Bates price, as a lot of yards use Bates' prices, to price their parts.
There is one other option, other than searching for smaller local salvage yards in your area, or ebay. You can go to TractorHouse:
http://www.tractorhouse.com/ And post a "Want to buy" ad there. Salvage yards normally contact you within a few hours, to 36 hours. Look on the left side menu, third item down. You'll need to register, and leave some contact info, and enter parts needed. They usually ask for a part number also. Since the Case/IH online parts store seems to have discontinued listing parts for the A, and only the Super A, it's tough to come up with a part number for the tie rods, unless you have a hard copy parts book. You can get the oem part number for the center steering arm from the Bates page, which would be 356554R1U. The center steering arm was different on the Supers, as they had a square hole. And appears the tie rods had automotive type ball stud ends, rather than the adjustable types on the A's.
Hope this helps..!!