Cheap agi can be found with
https://wiki.project1999.com/Serpentine_Bracer
But when I was searching for it I also saw this one, which you may be able to earn on your own.
https://wiki.project1999.com/Basilisk_Bracer (most accessible)
....
I did some more searching. Cloak of Leaves from named Treant in SK is cheap.
If you were willing to make the journey, you could loot the legs off the Newbie Beatles Queen in Field of bone for 5 agi. (easiest kill)
Giant Snakespine Belt might be the cheapest.
You really should learn to use the equipment search and sort on the wiki. It is an invaluable tool. Certainly could have avoided having to come to forums and got the answer yourself.
https://wiki.project1999.com/Equipment_By_Class