Check with your salvage yards locally then wherever is closest. Watch the wants ads and search the internet. Freight can add up if it's too far from you.
I had a wide front on a Super H and took it off because I didn't like the turning radius. It brought $500 several years ago.
A wide front end can lead to a false sense of security. They tip only lightly less than the narrow front ends if at all. A wide front end raises the pivot point about 2', point is it still pivots. Set your rear wheels as wide as you can stand it, load up the weight on the front and rear as much as is practical for what your wanting to do.
Most important is to use common sense.