Throttle locks can be had from several makers. The real question is what are you willing to pay? (I have Throttlemeister, no need to slip the grip off, it goes on the bar end, for $100+)
As to the grip, it's a slip-on over the throttle tube. To get it off you work it off by pulling on the end next to the starter button housing. By pulling toward you the grip expands (compresses shorter) and will slide glacially slow off the tube. To install you slip it over the tube end and push toward the starter house (again compressing the grip so it will slide). The process sounds easy until you actually do it, patience (or get a knife and new grips).