Use glyph of warding
If you cast glyph of warding and choose the option Spell Glyph:
You can store a prepared spell of 3rd level or lower in the glyph by
casting it as part of creating the glyph. The spell must target a
single creature or an area. [...] If the spell requires concentration,
it lasts until the end of its full duration. (PHB 245-6)
This will allow you to cast levitate and invisibility on a creature of your choice by casting the glyph on a book and setting the condition "target: the one who opens the book" or something similar. You will have to use your actual concentration for magic weapon, in your example.
The drawbacks are that this requires the expenditure of a level 3 spell slot, 1 hour of casting and 200 gp of materials per spell. If you know where the fight will happen (as the glyph cannot be moved (generally)) and prepare ahead of time, you might be able to spend the slots and time at an earlier date.
This may sound a bit cheesy, but the cost is really high if done on the spot and a risk to pull off or it shows proper preparation if done earlier (and it is not guaranteed than nobody will notice the inscriptions, depending on the site).
The description of the spell in earlier printings starts with:
When you cast this spell, you inscribe a glyph that harms other
But this has been changed in errata (ver. 1.22):
Glyph of Warding (p. 245). The first sentence clarifies that the
magical effect needn’t be harmful.