My dad made my cat tree for me and I covered the perches with carpet myself. It is fairly easy to do with two people and a good staple gun. Maybe you could revive yours with new carpet? I bought a large carpet remnant at a carpeting store for $10 and there is enough to cover my tree at least twice. Also, you could use sisal rope to cover the rough, worn wood if your cats are fond of sisal.

Just a suggestion. Here's a pic of the tree my dad made. I and my cats love it.