The best solution is to buy a tactical flashlight remote switch then reverse engineer it to fit the end of the spyder. Basically, if the end cap of the remote switch doesn't fit the spyder then cut its cable, disassemble the spyders end cap, then rewire it to work. Otherwise you are going to have to search for a flashlight with a 3/4 inch (18mm) end opening (any 18650 type) and hope the threads match on its remote switch (if it has one)
Well, I've already tried using the one from my other laser, but the thread is different, plus it would be a pity to ruin the original switch to use this thing only once...