Juju, I don't remember what year model you said your VTX is, but you can check out these. You can see the design is so that they should be easier to grab and pull. The only 'adjustable" ones that I have seen are like the ones my Goldwing has or Click & Roll makes them for some of the sport bikes. Good luck with them and maybe Zook can help out...
http://www.bikebandit.com/levers/c/a658113?mg=7766&t=1