Hello there fellow Sebenzanista! Nice idea, recyling the Sebenza clip, which is a super quality item like the ARC. I have a spare Sebenza clip but don't think most ARC owners have one.
For those without a Sebenza clip, I suggest a AAA Mini-Maglite clip which fits nicely with a little bending. I happened to have one and it works well. I found a clip supplier at "http://www.flashlights-store.com" under "accessories" for $.44 each.