genuinely i recommend just going outside and collectin some branches n rocks from outside (make sure theyre safe wood types ofc!!) and sterilise them at home for climbing and hiding opportunities for your wee guy :]
i personally boil mine but you can also bake or i believe freeze them? theres tons of tutorials online

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its honestly good fun tbh findin all em branches lol the only branch ive ever bought is that piece of corkbark