Until Tiablo has their own available, the Pacific Tactical Solutions 9H-tc tail cap tapeswitch/pressure switch is an easy mod for the Tiablo A8/A9 (fits both). You just need a small nylon washer to serve as an insulator around the contact button in the center of the tapeswitch (even waxed cardboard will due), and to solder a small compression spring to the contact (cannibalized, or from Ace Hardware). You could likely get creative and solder the spring to a small metal disc/washer that is a bit smaller than the nylon washer if you didn't want to permanently mod the tapeswitch. The P-T is a good solid switch unlike some of the airsoft switches that are available. I haven't tested for water-resistance yet, but the o-ring on the Tiablo appears to fit well. Alternatively, another nylon o-ring, or a thin line of clear flexible sealing compound in the lip overhang of the tail cap, looks like it would work especialy as you won't be changing batteries all that often if using primaries.