You could just make a script that casted a highlevel Spellresistance spell, from a cleric, and remove VFX and what not.
Actually, it's not that easy.
There are three "types" of spell resistance: Monk SR, Item SR and "Effect" SR.
The three types do not stack with each other. The first two do not stack with themselves either (you won't get 24 SR by having two 12 SR items).
What is very strange though, is that the "Effect" SR is actually stacking. Heh, the function to create the effect is even named: EffectSpellResistanceIncrease
So, yes, by scripting, you could technically make spell resistance stackable... i.e. you could make a stackable SR spell (can I hear anyone scream overpowered?

).
To make it stackable with Monk/Item SR one would have to do a few coding tricks. The first is not difficult, just check for the feat (I assume it's a feat giving that) and record the value. For the later, it's slightly more complex as one would probably have to loop through all items searching for any SR property for the value.
To make... say... the SR spell stackable with Monk/Item SR, it's simply a matter of applaying "spell + monk + item" SR instead of "spell" SR (or something).
BUT... A lot of issues quickly springs to one's mind... What happens if someone unequips the SR item? Should, for every unequiped item, the SR be recalculated? Etc, etc, etc...
So... um... while it is in theory possible to make SR stackable by scripting (I have yet to see something impossible... if one wants to put in enough effort!) it's in practice far too error prone (at least with a quick though of the matter) to be worth the effort.
