Lot's of people use bamboo in their cages from the store. We bought wooden dowels that are really cheap. You just buy a longer one and you can cut it to size and have extra for when you need to change them. I don't know about protecting it, especially with polyurethane. Just go with cheap wooden dowels.
We also went to the pet store and bought wooden ladders that go in a birds cage for our 2 panthers to perch on. They LOVE them. The dye does run off but it's safe for animals and it never affected the chams. They're inexpensive as well and very sturdy.
Its important that you know that "lucky bamboo" which isnt actually a type of bamboo is toxic. But real bamboo is fine.
No problem for the bird ladder idea! The best part is they come in different sized and thicknesses. So depending on your chams age/size you can get ladders with thicker dowels in between or thinner. Our chams are obsessed with them and bask on them all day long. Shooter loves to stick his head between the dowels and check you out haha.