Why not see what the company made to fit the model you have over what span of years. You probably will find it's a long span. Then set up an Email search on all the regional Craigs lists . When you see one jump on it. I see a lot of small Kubota hoes kicking around all the time . People buy them use them a few times then decide they don't use them enough to keep tripping over. You can find real nice ones for about $7500 (which is about all they are worth anyways).
Mine came with a sub frame mount and is nice because I can take mine off in about 10 minutes. We got ours at big discount from Massey due to having horses -28% discount that brought it down to about what it is worth. For some reason or other they were awash in the things the last few years. I had to wait for them to literally cast mine last summer. Nice to have though and many a stump has fallen to it. One thing for sure. You definitely should have a sub frame rather than a 3 pt setup. Mine bounces around enough digging in the tough ground we have here . All that twisting and yanking might just break something important back there where mine will easily pick up the whole 5000 lbs worth of rig and drag it nicely around. Too bad they're suddenly so darned expensive, they sure are handy if you own a large piece of land.