You've got most of the options right there. There are a few others, although none are nearly as convenient:
- A Necromancy Wizard can have 1 of any type of undead using their Command Undead feature.
- Similarly, the Dominate Monster spell can potentially let you have any type of undead.
- The Shapechange spell lets you turn into any type of undead - it also lets you turn into a shadow dragon, to create shadows under your control with Shadow Breath, or a Wraith, to create specters under your control with Create Specter.
- A Moonblade, with the right properties, will let you have a shadow for a minion.