For the life of me, I can't figure out why anyone would want something sticking off the twistgrip like a tumor. If you negate the spring tension the return spring on the throttle bodies pose, that's really all you need. HD has had a friction snubber on their bikes for years. Personally, I can't see spending even 12 bucks on a tumor when for 50 cents you can achieve the same result.
I have mine set in a completely neutral position. I can ride down the road and take my right hand off the throttle and pick my nose if I want to and the bike maintains it's speed, gradually slowing down after some distance. I find the stock grip rubbers to be quite comfortable but the 50 cent throttle lock will work with any grip so long as you use the stock bar ends. All the add-on tumors remind me of banjo picks with a tail.
My design is completely hidden, flush with the twistgrip. You don't even know it's there. I guess if you want to spen a hundred bucks, get a Throttlemeister. Mine does the same thing for a hundred less. Of course you have to make it yourself....that could be a problem, I guess.