But why?
Standard shock pumps typically go to around 300psi. This is fine for air can inflation, but for shock servicing, much higher pressures are needed to charge the IFP, particularly in [shocks that feature a lockout]- faqload.com/faqs/bicycle-components/suspension/monarch-rl-2015-rapid-recovery. Some of these shocks will need around 500psi in the IFP for the lockout and/or pedal platform to work properly.
600psi
The Rock Shox 600psi pump is a pretty basic affair. Its got a 600psi gauge and a small diameter piston with long stroke to make getting up to 600psi less of a chore. There's a small pressure relief button near the head and a swivel tube with a nice long engagement. That's pretty much it.
Being more of a "specialist" item, these high pressure shock pumps are bit more expensive that the normal 300psi versions. Expect to pay around the $50 mark.
For IFP inflation when servicing Rock Shox shocks you'll also need the IFP fill adapter.