Where do you get your cork rounds from and are there alternatives?

I've been looking around for some nice medium to large corkrounds for my leachianus. Where have you guys found to be the most affordable place to get them? Are there any alternatives, maybe a DIY PVC tube or something similar?

I have used large diameter PVC as snake hides, but i have access to a machine shop. It could be done by hand but it would be a pain

I have a chop saw that would work, but I want it to look natural. I'm not sure how to do it.