I have always used salvage yard factory parts for outer swaps, have had no problems doing do. You can search car-part.com to find some, you need from a 92-94 Trooper to get the right length.

I also have heard of aftermarket CVs that are specifically made for replacing only the outer, presumably with the right ball pattern to match the inner etc., but I have not tried these. Don't get an entire aftermarket CV axle, because they often will use whatever joint design they feel like, so it probably wouldn't match up with your factory cup.

Steve Carlson - 95 Trooper LS expo rig
Serenity now!