Expanding on a comment I made with additional solutions:
Dominate 5: Possession
Get/Sculpt (Plastic surgery/Vicissitude) a body double and possess them, preferably a ghoul for additional durability and access to basic blood use and some low-level physical disciplines.
With sufficient successes when you possess someone you will be able to use Auspex, Presence, Dementation, Dominate, Chimerstry, Necromancy and Thaumaturgy with no risk at burning up at all.
Quoting from V20:
The character may travel as far from his body as he is physically able while possessing the mortal. The vampire may also venture out during the day in the mortal form.
However the character must be able to stay awake in the first place (as for any of the other solutions!)
Animalism 4 : Subsume the Spirit
This allows travel around in the day in a very similar fashion to possession as an animal.
Necromancy The Corpse in the Monster: Gift of the Corpse (4)
This only lasts one turn per success, but for that duration:
Sunlight does only bashing damage, and then only if bare skin is exposed on a clear day.
So this will be fortitude soakable etc. Very short duration however.
All quotes/powers listed are from V20.