welcome aboard.
As mentioned, Zofia of Poland was offered OTL. But there was also Zofia's cousins, Margarethe or Katharina of Saxony (OTL electress of Brandenburg or duchess of Munsterberg), who would have a "higher" claim to the throne of Bohemia- unless you accepted Zofia's mother's reasoning that her kids were the rightful heirs- could've been offered. Maximilian would be a damn sight higher than Katharina's OTL husband.
There could also be Ludimila of Bohemia (Jiri of Podebrady's daughter). This is less out of left field than it might appear. For the Habsburgs, getting the Bohemian electoral was sort of like the great white whale. So, if - once Zofia's sister, Jadwiga, snaps up the duke of Landshut (Ludimila's original betrothed) instead- Jiri opts to marry Ludimila to Max (as part of a Habsburg-Podebrady succession pact), it ties it up nicely. Poland will likely object, but given that they're unlikely to ally with Hungary (the logical choice) due to Queen Elisabeth's low regard for Matyas Corvinus, it's pretty much a given. After all, Ludimila's sister, Zdenka, was married to one of Friedrich III's most loyal generals (Albrecht of Saxony)
