Flower pot drainage material?

packing peanuts work nicely.

Styrofoam packing peanuts allow drainage.

Try coffee filters.

you can use crumbled up foil, or anything coarse that will not disintegrate too much, also broken up plastic etc.

Packing peanuts, water bottles, soda bottles. Fill 3/4 of the way with filler then add the potting medium. If using succulents, they are shallow rooted and that will be more than enough soil for them to grow. Just know it will be top heavy. I would build in place.

I'd suggest large pieces of styrooam be used rather than the packing peanuts unless you also add some type of landscape fabric over them. I did the peanuts a few years ago and after a major rain, they floated to the top and overflowed onto the patio. What a mess! Just the voice of experience. :)

I use empty pop cans, sort of crumpled up, in the bottom of my big pots.

In large pots the peanuts can be used, just contain them in mesh bags to keep them contained.