I want to fill the magazine of my deactivated guns with inert ammo however I don’t know witch ammo is correct ?

There is a cz27 pistol
Ppsh-41
Stv-40
Mosin-nagnet
K98
Sks
M56 smg
Akm
Bren gun mk11
Hotchkiss universal

I want to fill 1 mag of etch gun ? However I’m confused what ammo I should buy ? Also can some one give me a rough price guide for the ammo …