Spicer makes a replacement U-joint that looks almost identical to the original except that it uses inside C-clips but they are barely visible when the driveshaft is mounted. Keep in mind, the originals used no clips at all and were simply held in with the plastic injection. Unfortunately, unless you can find some NOS (assembly line U-joints) and someone who can do plastic injection, this is as good as it gets. These U-joints also have no grease zerks like the originals as well though they can also be purchased with zerks if you prefer them. When I restore my shafts, I try and leave the little red plastic tab in place and just remove the plastic from within the groove. Then we press in the new U-joints. I can check for you tonight and get you the spicer number for the U-joint that you need as I don't have it with me at the moment.
Rick