The Brit tractors with that left hand brake used a bevel gear on the pinion shaft to hold the tractor. It was a superior system of a parking brake. But it would require a split between the tranny and rear end to install all the parts, would be pricey and was prone to letting water into the rear end oil when the seals wore out.
If you are fat and lazy like me look for the parking apparatus from a 3600 to install on your 3000. It was one of many small improvements the X600s had over the Thousands,
Uses about the same T handle but it is mounted higher up on the side so you don't have to reach over so far.
You'll have to do a bit of tinkering to make it work on your 3000 but not hard and definately worth doing.