Thank you!! I mostly used this wide cardboard that is used for packing, it's so "crunchy" and easy for tearing, the birds adore it! Also has some very thick corner cardboards. Some wooden beads, wooden blocks i picked up at pet supply store, coconut shell... And coconut fibre ropes
And I embedded your idea with the muffin paper liners - its perfect for hiding some treats there!
Also one of them has a big piece of wood with bark, also got it at the pet supply store.... The budgie was working on that one furiously hard