Can anybody recommend a good sofa bed? (or a good sofa bed hack)

I want to put one in a spare room. I know usually the problem is that the middle bar is uncomfortable as hell, so maybe now there are models without that?

Another thought was to get a pretty thick memory foam mattress topper for another bed the same size, and when guests sleep on the sofa bed, I can put that on there to maybe mitigate the bar issue?