You might check with
http://www.dexteraxle.com/
I bought a complete new custom length axle a few years ago for my race car trailer. Price was surprisingly low considering that it included everything other than wheels. I had electric brakes, drop stub axles, bearings, hubs, and maybe even new u-bolts. Mine is a 3500 lb single axle. As I recall it came UPS (I did NOT have to pick it up).
There is probably no need to "make do" with whatever you can find at various local sources if you can find EXACTLY what you need directly from Dexter.
Dexter is good about spare parts also. The website HAS lots of pictures to help id what you have since there are LOTS of different axles and styles.
http://i.b5z.net/i/u/1080235/f/Appl_Manual_4-04.pdf
Also, try getting a parts and accessories catalog from one of the big RV and travel trailer dealers. These frequently have a lot of axle and brake related stuff, including illustrations.
FYI my understanding is that you do NOT want take off mobil home delivery axles!!!!
Dick