Either a bolt down or hidable/disguisable safe.
https://www.amazon.com/First-Alert-Waterproof-Fire-Resistant-Combination/dp/B008ELITP0/ref=sr_1_4?dchild=1&keywords=First+Alert+2096DF+Waterproof+Fire+Safe&qid=1623121359&s=hi&sr=1-4
https://www.amazon.com/s?k=First+Alert+2096DF+Waterproof+Fire+Safe&i=tools&ref=nb_sb_noss
https://www.thehomesecuritysuperstore.com/collections/hidden-safes
https://www.thehomesecuritysuperstore.com/collections/safes