Total posts : 45366
I am surprised that you have had trouble finding the PVC coil form material. Here, it is available at hardware and “big box” home improvement stores in three foot lengths. I used 3 inch schedule 40 drain pipe. Even if you have to buy a 10 foot length at a plumbing supply store it is not too expensive.
Here’s a link to an inductor design calculator which I have used. It is accurate according to my measurements of the coils I have built.
You can use this to design your 2″ coil if that’s what you want to do. Just enter the data for the 3″ coil to get the inductance and work from there.