Stop by your local auto upholstery shop and have them make you a custom set of head rests to match your interior .building anything that requires "Rube Goldberg bracketry" to hold it in place just adds to the potential danger of impaling your head .They can build you a set of head rests from dense foam and have them attach with Velcro that could be stored by folding them down behind the seat when not in use .THINK LOW TECH . adding suction cups or hard mounts is just asking for a serious headache even in a low speed hit ! You can't build conventional type seat mounted head rests on buddy buckets because they just don't have the metal structure internally to make them secure .
