Ny neighbor and I built that perch and it needs recovering now as they have really used it a lot! We built Rie one the other day and I am waiting for her to post pictures of it finished but here is one of it just cut out and propped up....

The round part is one of those spools electrical wire comes on and if you go to your local lumber yard where they sell wire, they will give you one if they have a empty spool... or know any electricians. They just throw these away when they are done with the wire... I had to buy the 4X4 and "L" brackets but we had everything else. You cover them however you like.