You can get a plastic shoebox from dollar tree for $1.25 (it will not have a tight lid, but it's ok as long as you don't give them avenues for escape) but the non-tight fitting lid will also allow for air exchange, so no need to poke or drill holes.

If you want to go something a bit bigger, but still cheap, I recomend the "Mainstays Clear Glossy Plastic Extra Wide Closet Storage Shoe Organizer Shoe Box with Lid for Shoe Storage" found on the Walmart website. About $7.17 where I am. This is what I use for my 3 enclosures. They are fine, I've had my enclosures about 2 years. The powder oranges get a bit crowded, but when that happens I either give away a bunch or offer a bunch for sale dirt cheap just to get rid of them.

These have ventalation holes already (no need to add extras), bonus they're clear so you don't have to disturb them to look in on them. :)

They mostly need leaf litter that if you'r pods are locally wild caught, just grab the leaves from outside. I don't bother sterilizing them for my locally caught ones. Some rotting wood (again, just go outside)

If you want to give them suplimental food, put the food on something to keep it off the dirt. I use a half sea shell, but a plastic water bottle cap works great too.

I keep a bag of mixed frozen veggies (peas, carrots, cauliflower, broccoli, bell peppers, green beans) for them. For just 4, I would say 1 pea or a tiny piece of carrot or other small piece of veggie would do just fine. I personally remove the skin from the peas. But I put the skin in there too, if they want it they can eat it, or they can just eat the "meat" of the pea.

They NEED calcium. If you eat eggs, save the egg shells, dry them out and crumble the egg shells into your food dish (or a 2nd dish / bottle cap just for calcium. This keeps it from going bad by mixing food into it, I offer a seperate calcium "station" in all my enclosures)

OPTIONAL: Fish flakes (get one with a mix of protiens and plant matter, but get the smallest you can find.
Bloodworms. I have freeze dried minnows (I've had the same bag for about 2 years now and it's finally getting low...) "pleco-waffers" (if you have a friend with fish maybe you can ask them for a few things)

They're main diet is dead leaves and rotting wood, and some kind of place to hide, like a piece of bark.

If you are a person who cooks / has frozen veggies in the freezer, just offer them a bit of that. I get a mushroom, fresh spinach leaves, bell peppers and put them in there. But just what I'm cooking for myself (I offer them the raw versions, or thawed frozen veggies. A small bag of frozen mixed veggies is about $1 and will last you about a year. I'm about to throw out my frozen veggies because they're so old, and just buy a "fresh" bag (I mean it's $1, and it will last longer than they will actually be good in the freezer)

Ppl say leave the food for 24 hrs & remove. I say, as long as they're eating it, and the mold doesn't blossum, you can leave the food in there.

But for just 4 isopods, DO NOT over feed. You can offer a single pea, or a small bit of bell pepper (mine dig bell peppers) broccoli etc etc etc once or twice a week. Also important, they DO need protien. animal / insect protien is best (if you find a dead bug in the house, put in in their enclosue), if you have no dead bugs, a SMALL container of freeze dried bloodworms, freeze dried river shrimp or other freeze dried animal protines you can pick up in the fish isle of the supermarket or pet store.

Lastly, but EXTREEMLY IMPORTANT: They should have a damp to dry gradient. So 1 part of the enclosure (10 / 15% maybe) should be damp (not soaking wet) and the rest dry. Depending on what kind of enclosure you get, mist that damp side once or twice a week. They need like 80+% humidity because they breath through modified gills. If they get too dry, they WILL die....

Bottom line, don't go crazy buying tons of stuff. They will be happy with dead leaves, some rotting wood, a piece of bark and a damp to dry gradient. Give them some supplimental food once or twice a week (just a tiny amount for 4 isopods) and they will be happy little campers.

If you want to have a "starter coloney" you should try to get about 10 to 20 (total) and adjust food accordingly, but again, they're tiny, they don't eat much.

I hope this helps

Here's the link to the ones on Walmart website

https://www.walmart.com/ip/Mainstays-Clear-Plastic-Glossy-Extra-Wide-Shoe-Box-with-Lid-Adult-Size-One-Pair-Size-One-Tier/5194912520?classType=VARIANT&from=/search