I've no idea where anyone would buy one of these, I reckon you'd have to join a Men's Shed and build your own.
Personally I just put a cushion behind my head and let the guy sit on my face, I've had men over 20 stones sit on my face no problem, maybe use two cushions for them and position myself between a stool and my bed so they can use their hands to lower themselves down and get up.
