Good luck with your new tractor. There are a lot of aftermarket loader manufacturers and a wide range of qualities. You can spend whatever you like; the market is competitive. I thought I had a list of a dozen or so but cannot find it. I do recall several makers were in Washington state, one in Kansas, and several really nice loader makers in Canada. Westendorf is maybe the dean of nice heavily built aftermarket Ag tractor loader makers - this is their 90th year. Located in Onawa, IA.
You want to get some sort of Quick Attach FEL bucket so you can swap front implements. Get a bolt on cutting edge, and a heavy "dirt bucket" rather than a lightweight "materials bucket".
Most loaders mount by bolting or clamping their uprights by bolting to a mfg. supplied subframe that runs most of the length of the tractor. The loader bolts to the subframe, and the subframe then bolts to the tractor at both ends. That way the loader stress is spread out, and having various subframes allows the same loader to be sold for a series of different tractors.
There's more to the best loader than that, but that will get you started.
luck,
rScotty