Here’s an example of a rubber “grommet” or “tail-standing rubber boot” used on the EagleTac P20C2 MKII flashlight. It simply slips over the end of the tailcap. With a little imagination, one could come up with something similar. Even a rubber hose of proper diameter and cut to the proper length should work.
See last pic borrowed from Amazon.com: Other users are reporting that a one inch diamter pass-through-bushing (the kind used to pass cables and etc through walls, tabletops, etc) are fitting their PD35 tailcaps.
