One thing I did recently was take an old sweatshirt my boyfriend was going to give away and cut the sleeves off, and the end of the sleeve to make a tunnel, then take craft wire, make it a little longer than the length of the entrance to the tunnel, double it and twist it together then make a cirlce. Sew it into the edge of the tunnel, then make another wire circle, do the same to the other side, and sew fabric loops on the top to hold your metal clips that will attatch to the cage. It was free for me to make, the wire might cost a little, but Its a ton cheaper than buying premade stuff.