I had a standard plastic non-adjustable Go Cruise that came with a used bike I purchased, it did not hold the throttle very long either. When I purchased one for my F6b, I got the adjustable, aluminum model. I holds the throttle very well. Not the best throttle lock I have owned, but it requires no alteration to the grip to install and works OK.

Another accessory that did not work out for me -Mustang seat - The lower seat position increased the bend in my knees and made my legs comfortable. But, the lower seat position was fun to ride in the twisties.

Shark Skins (original Grip "Bubbies") - I got them to help with my hand numbness. They did not help. My guess is nothing is going to help my hand numbness. I think it is nerve damage from years of riding a bicycle. But, the foam is better than the Grip "Puppies". It is closed celled on the outside and is not as spongy. I am going to place an ad for them soon, $15 including shipping. Original price, $25 online.