I've wondered if billionaires get their jets lined with lead.
Lead is notoriously heavy, but if you buy a 737 and it only ever has to fly you and a couple other people, it might be feasible.
Or I guess they could just line one section where they spend the majority of the time.
hmmm...
looks like there's something called ultra-high-molecular-weight polyethylene.
"UHMWPE/hydrogen-rich benzoxazine composite (UHC) exhibits excellent cosmic radiation shielding."
maybe that should be a thing.