I use a cramp buster. http://www.crampbuster.com/
It's cheap, it works great for me, what more could you want? I think throttle locks are ridiculously dangerous anyway. I was part of a group ride about 5 years ago and saw a girl wreck using one. She died 2 days later from her injuries. From what she said, and what was pieced together after the fact..... There was a red Ford F150 extended cab, 97-04 body style, that pulled out in front of our group as we were going down 287 South towards Fort Worth. We were all riding in the right lane and a group of faster cars was overtaking us on the left. The guy in the truck just froze. He got out into the lane and just stopped. There was cars in the left lane, and the truck was taking up the entire right lane AND the hard shoulder. There was nowhere to go. You had to stop.
We all managed to get stopped before hitting him, all of us but her anyway. What seemed to be the biggest contributing factor of her accident (apart from the truck) was that when she jumped on her brakes (panic stop), she just didn't remember to unlock the throttle. That on its own wouldn't cause a major problem in itself because you can just roll the throttle forward and close it without unlocking it. But, because it was a "no time to think or prepare" situation, that action, unlocking or rolling the throttle closed, just didn't happen. She just didn't do it. She forgot. In her rush to get stopped the throttle didn't snap closed on its own like it would every OTHER time. That little push, only enough throttle to maintain a 70mph cruise, was just enough to make her stopping distance slightly farther than the distance between her and the truck. It was CLOSE anyway.
IMHO, if you use a throttle lock, you should never NOT use it. It MUST be instinctual. You must be able to operate it as you would your brakes. If you think "I will just pull in the clutch and then it doesn't matter" you have never had a "going to meet my maker" moment. Most people who have been in an emergency like that know that often times, you don't even have time to pull in the clutch before getting on the brakes. A lot of the time you are well into your stop before you get that clutch in.
If operating a throttle without a spring-return is not completely second-nature, when an emergency comes up, returning your throttle to idle manually will not happen. When you lighten your grip to let the throttle snap closed just as you start to brake HARD, nothing happens, the motor just keeps charging ahead.
If your hands are really bothering you after, well, after ANY amount of distance, you should look very closely at some other things than a throttle lock. Most importantly, are you holding the bars too tight? I did. I had to make a real effort to let off and not grip so tight. I'm not talking white knuckles, but holding on any tighter than it takes to keep the bars from slipping from your hands is too tight. Second, it doesn't matter what kind of bike you ride, if you are going any distance whatsoever, your wrists should be STRAIGHT. Most people ride with their hands tilted upwards, so their wrists are bent at about a 30-60 degree angle with their knuckles higher than their wrists. That's wrong. You should be able to tie a metal bar to your forearm and to your hand and ride that way. The line from your forearm to your knuckles should be perfectly straight. If it's not, you need to adjust your handlebars, get some new bars that fit YOU (different bend, taller, shorter, wider, etc), get some adjustable clip-ons (for you sport folks), scoot forward, scoot back, do whatever you need to do, just keep those wrists straight. I can't overemphasize how important that is. It's super important for all riders, but even more so for sport bike riders because so much weight is carried on the wrist and the higher vibrations of a tight suspension. If your wrists are sore after a ride on your R1, CBR, GSXR, etc, get some adjustable clip ons, get those wrists straight, and that sh!t will STOP, I promise! If you don't, and you ride a lot (like I do), you end up with Carpal Tunnel Syndrome. I had to have the surgery twice. Then I finally noticed (even after I had heard the same thing I am telling you a hundred times) that if I kept my wrists straight, I could ride for hours, days, weeks, at a time and have NO Pain what-so-ever! After some new bars and clip-ons, I never had another problem, ever. Plus, if you look at braces for CTS sufferers, they all do one thing, they keep that wrist STRAIGHT.