help with modding chinese h14 clone

hi i am trying to sort out a external battery pack for this cheep led lenser clone so i can fit 4 18650 batterys for longer run times and so i can put it under a jacket for extreme cold weather. but the issuse i have is the switch its in the battery box on the rear of the torch was wondering about fitting a inline switch but its a 3 mode torch and i am abit lost as to what switch to look for.
any help would be very welcome cheers