Can I reduce or eliminate water hammer without plumbing?
Pretty much, no.  To reduce the noise you need to secure the pipes properly within the walls, and add pressure-relief tubes to the pipes that hold air in them beyond and above each fixture.

You cannot affect the pressure within the closed system of the plumbing by changing something on the outside of the system...  so at a minimum you have to at least open the walls - something the landlord will frown on...