Hi there, I've seen slides on eBay when searching for bird toys. They are small and inexpensive. You could try entering 'bird slide' in the search bar on eBay or just 'bird toy' and scroll through all the different listings that pop up.
I'll see if I can find a link for you. I'm in Aus but I'm sure the seller was from China or Hong Kong and ships worldwide. Bear with me though, it may take me a day or two because I'm going into hospital for a procedure, but I won't forget.