Did they put 4.10 in a lot more rear wheel drive trucks? I'm assuming a fair share of 2wd 2.3 had them. I've found plenty of 4.10 8.8 but not very many d35.
I think some 2WDs before '93 got 4.10s, but they will all be 7.5" axles.
4.10 D35s no doubt are rare.
When it comes to finding rare parts, I've had decent luck with
www.car-part.com. I found my 2.9L 4WD-version M5OD through the site (only came in select few 1990 trucks, mostly Supercabs from what I've seen).
Put in the search for a '91 or '92 4x4 Ranger and select 4.10 front axle assembly. Should come back with all D35s if there's any near you.
Edit,
Nevermind, OP said he already did that.
I just did it myself and it came back with four in the whole USA & Canada.
Unless you want to have one shipped, maybe try the "Request a quote from hundreds of recyclers" link? See if that yields anything?
IMO, I think the best way to a 4.10 D35 is to do like Downey said and just regear one (and make real sure 4.10 is really what you want, because 31s is about the biggest tire 4.10 is real great for. Any bigger tire and you might as well go for 4.56 or deeper if you're going to regear an axle)