Can I ask what you've read about PVC piping that's made you change your mind about them?
Also, ferret tunnels are a popular option. They come in fleece, plastic tubing, or a crinkle material. I got the Super Pet Crinkle Tunnel for my hedgehog and she absolutely loves it. I just throw some fleece strips in there and she loves to burrow in it. It's also pretty easy to clean, though it's absorbent (but dries quickly).
I love my little Tansy [1.3.14] <3
& my boys, Wally [10.6.10], Runner [12.16.2004] and Champ [11.10.2003]