There is an after-market two-stage switch for all of the Surefire E-series LED lights. It's called a McGizmo McE2s switch, or Aleph E-series 2-stage switch. Unfortunately it is out of production, but you can still find one every now and again on the B/S/T boards here. I would also reccommend putting up a WTB in the Buy section, someone may have one they're willing to part with. I have one for my L4, and I found it here on B/S/T.
Good luck,
Josh