Well I use ADOX and Rollei 120 and the film comes in those nice cans. I have also made them by cutting the bottom out of a 35mm can and then taping it to another 35mm can with black tape. I quit using the ones I made from PVC pipe as they looked too much like pipe bombs.

The thing though is I put little rubber O rings in the caps of the PVC ones to make them water proof.