If you want the proper one you need either the
Tamiya Shock Pump or the
Ride Air Remover.
If you want an vacuum pump for a fraction of the price of the r/c car ones, get a Vacuvin Coffee Saver and make a platform for the shocks to stand in. I made a stand for my shocks from a square of styrene sheet with 4 holes in it for the shocks to hang from with two strips in a T shape to hold the square up.