brand new to isopods - getting food from outside?

tl;dr - are there some good things i can find outside for my isopods that they'll like? and if so, what precautions do i need to take to make sure it doesn't hurt them.

hello all! i've had isopods in my turtle's bioactive terrarium for about 6 years now. and they are SO cool and even more helpful! i need some more as i did a whole dirt replacement in the turtle enclosure and unfortunately didn't pick enough out and the pods are all gone. :(

i went to a more specialized aquarium/reptile store and asked their opinion on what ones to get that repopulate fast and can handle a bit more dry climates (never completely dry, always a moist side) and am learning about these guys a little more.

the guy at the pet store told me to get red panda king isopods as that's what he uses. but my turtle could possibly munch on them and from what i've read they might not be the best at reproducing. and they're so cool looking that i'm accidentally an isopod keeper now. thinking i will get some from smug bug i think for her terrarium, and keep the red pandas as pets!

that being said, i've looked at some care guides and watched a few videos but this wasn't covered. i know they like decaying wood and leaves, but how do you get that safely? i'm worried there'll be other bugs that are harmful to them in the leaves/wood. i do know about pesticides and wouldn't take from anywhere near residential areas that aren't my own backyard.

are there some good things i can find outside for my isopods that they'll like? and if so, what precautions do i need to take to make sure it doesn't hurt them.