Dendo;
I don't know of a factory replacement arm that will work for you.

First, take a look at your drag link, is it fairly close to parallel with the frame rails? If not, that's probably the cause of the bumpsteer. There's a couple of things that rodders have been doing for years to correct this:
1. You can shorten your stock pitman arm by cutting, and re-welding it. I took mine to a professional welder and had him tig weld it and put a reinforcement plate on top of that. It's stronger now than a stock arm. I wouldn't take much more than 2" out of it as you could shorten your turn radius. I took 2 1/2" out of mine and can still turn lock to lock.

2. You can heat and bend down the drivers side steering arm (where the drag link connects) but make sure you have clearance all the way around before you do this.

3. I hear you can also "flip" the drag link to steering arm connection but I've never tried this. There was a post on the forum here not too long ago about doing this.

4. Another thing you can do is relocate your steering box higher off the frame using a homemade bracket. I've got a picture of the one I made somewhere in the dropped axle album.

The goal is to level out that drag link. The closer to level, the less bumpsteer you'll have.