Sure you can ...get the P/S pump from, say, a non-SLS 400E and its rear shocks. That'll work.
What is wrong with yours? The N2 cells are pretty cheap but the hydro-struts aren't at 700$+ each. They usually should last a good long time with regular fluid maint. of the system....at least 180K miles. Mine is still happy at 145K. Knock on (burl)wood...
