I want to have my players travel through the Elemental Plane of Fire for a short period of time. None of them are immune to fire damage. How could they prepare themselves to survive this ordeal?

We have a wizard, a bard and a monk. They will be traveling with a Fire Giant to guide them.

I found the Resilient Sphere spell that the wizard could learn. I could drop that in as a boon for an earlier quest so that they have it handy… but I’d like some other ideas.

How would you handle this?