Other food rich in potassium (and therefore in 40K) include potatoes, kidney beans, sunflower seeds, and nuts.[18][19] Brazil nuts in particular are not only rich in 40K but may also contain significant amounts of radium, which have been measured at up to 444 Bq/kg (12 nCi/kg).
https://en.wikipedia.org/wiki/Banana_equivalent_dose
(The relevant bit is at the end:
Fill your bidons with loose mash. )