Actually, the bucket on my Kubota B219 loader is just 38" wide. I don't think they make them that small any more. The reason my Father in law got the Kubota B6100 and this loader back in 1978 was that he needed something to get into back yards to do landscaping work - through existing fence gates.
I would think that someone would be making a loader smaller than 48" these days for the same reason. There aren't too many fence gates in suburbia that are over 48" wide.
How about a second bucket, maybe a used/twisted/otherwise junk and have it cut down in width and rewelded? How wide is the rest of your tractor?
If not that, how about a cut down rear blade? Use the FEL to dump the material in front of the door then turn around backwards and push it in.
I know how you feel about wanting to do as much with the tractor as possible. If you have a farm implement junkyard nearby, you can probably come up with all sorts of ideas.