You can get sets of robes as sort of rare drops in the underground pass quest, possibly also rare drop from monks of zammy near dark wizzies (not sure about that though just a guess)

Just going off http://runescapeclassic.wikia.com/wiki/Iban_disciple

I am Post quest, completed it a while ago, only picked up a few robes at the time

This is on my main so i finished it for the heroes quest.... that sucks...Gotta have another guy get those quests done...Will probably just keep him camped there to since i dont want to get theiving up to 50 again too boring.

Yeah tried killing the necromancer a few times, but they are annoying having to kill 6-7 zombies before you get one kill.

I decided to run two characters (3 with my main following) through the quest line (not recommended...those traps...lol with 1 agility..) So i have them setup inside there, i can just run my main through the shortcut as i have 50 theiving and can collect an inventory then port out.

So if anyone else is looking for getting some, let me know, just make your way through it and i can kill a bunch to drop them for you.

Monks should always drop them aside the ones outside of the underground pass.

They do if you havent finished the quest, but apparently here at least (not sure about RSC never was a member) if you finish it, they no longer do.  Not sure if its a bug, or intended to be that way, but I have a work around now just leaving an alt in there, since there is a food spawn, can just train in there as well.