Is there a way I can refuse entry to an area with a spawner unless a char is carrying a certain item?
I know there are a few ways of doing it but I can't seem to get the GETONCARRIED variable to work with the spawner, even if it did work however I'd still not have a clue on how to make an area inaccessible.

Set it up for proximity triggering with the range set to what you want.
Use as a NoTriggerOnCarried string something like

youritemname,itemtype

set SpawnOnTriggered to true in order to get immediate spawning

Use a spawn entry like

SETONTRIGMOB/location/(x,y,x)

where x,y,z would be the location that the player would automatically be moved to if they triggered the spawner which would happen if they were not carrying the item. Note, you should make this location out of triggering range of the spawner otherwise they will be trapped unless they tele or recall out of range.