Quadratec is the only place that sells 4340 27 spline shafts. They retail at $329.
This is much more then a c-clip eliminator.
You can't just "catch a shaft" before it breaks. Once it's broke it's broke. You get to spend another couple of hours holding your group up while you dig pieces of axle shaft out of your diff and pound the broken piece out of your locker or carrier. By doing it this way not only do you get 4340 chromo shafts, you get shafts that are beefed up to prevent bending and flexing which is what kills dana 35 shafts anyway. Also this requires no modifications to your housing. You could very easily undue it and go back to stock shafts. I'd much rather "limp" out and home in 3wd then spend 2 hours holding everyone up while I attempt a trail repair.
I wasn't talking about catching it midway although it may have come out that way. I meant catching it before the shaft walks out. Even with beefed up shafts though the D35's axle tubes do flex a lot. This is what causes the side and spider gears to grenade. ARB used to make a C-clip eliminator. I'd be willing to bet Superior bought the rights. The C-clip eliminator had you cut the clip slots off your axle shafts and bolt bearing retainers to the ends of the axle shaft. This was done since they didn't want to redesign the ARB for C-clips. They changed their minds... I'm guessing Superior just mills the ends off their standard shafts. To swap back you'd need to unbolt the bearing retainers, swap back to the original bearings on both sides then swap both axle shafts back in. If you're running stock shafts, you won't have to mess with the good side.
If you're breaking 4340 shafts, c-clip or not, you're probably ready for an axle upgrade. At least when you're running C-clip shafts, you can attempt to fix it at the trail head or at a base camp. With either brake you're limping back to the trail head and I'm sure you're group isn't going to just leave you to limp back on your own. For many of the guy's out west, home could be hundreds of miles away. 2 hours fixing it to 100% beats trying to drive it. I guess if you happen to live near the trail or have a trailer queen then it becomes moot.
If there was such a demand for the C-clip eliminator it wouldn't have disappeared off the market for 15 years.