I'm very familiar w/ black maple (Acer nigrum) as I frequently search for this species every time I'm out in the woods. Most of our native hard maple is sugar maple (Acer saccharum), but I stumble upon A. nigrum multiple times every year when conducting field work.
Unfortunately, I don't have a source of black maple fruit for you. Black maple is definitely more prevalent in Iowa (central; west-central, and western). Therefore, you may want to try reaching out to a nursery in Iowa for some seed. Another option is to contact Possibility Place Nursery here in Illinois...I know they sell A. nigrum seedlings:
Best of luck!