The best way to approach this is to find a bunch of different types of suitable metal (windshield wiper inserts, sweeper bristles, maybe hacksaw blades, etc..) and a good number of different locks and just start making tension tools that fit those locks. If you do this enough, you'll have a good variety of tools that you can choose from depending upon the lock you're attacking. Basically you're looking for the "best fit"; something that doesnt interfere with picking, but fits great in the plug. You want to minimize wiggling and slippage. Tension tools really are an experimentation thing. Luckily, they aren't too hard to produce and don't take much time. I recommend experimenting with different end-shapes like tapers, serrated, short, long, twisted ends, blocky square ends, etc.. Who knows, maybe you'll discover something new and innovative. Good luck
