Depends how much it needs to fold.
We love the Re-Creation pocket spring mattresses we have bought from Vanrest in Melbourne. They fold much the same as a foam mattress of the same thickness, but only in one direction. Have had 3 now. One in a rooftop tent (100mm single sided), one on our bed at home & one in our Tvan. If you are not in Melbourne there will be other places nearer to you who make similar. The 'bendability makes getting them in/out of limited spaces much easier, & we find them very comfortable & a bit cooler to sleep on in hot weather (than foam). Cost was pretty close to what you would pay for high quality foam + topper + undermesh.

I'm surprised Makin' Mattresses don't do them ...... unless you need them bendier?

bedsdirect.com.au/products/re-creation-mattress/