If not Waukesha Sports Cards, then induction weekend in Cooperstown would be another possibility. For years Willie Mays would set up shop at some location on induction weekend. For a few hundred Mays would sign your item. If a promoter gets Aaron it would likely be MAB Celebrity or Jack Berke sports.
A link to some of last years signing on induction weekend.
https://www.uticaod.com/blogs/201807...in-cooperstown
MAB's Hall of Fame spectacular:
https://mab-celebrity.com/hall-of-fame-spectacular-2