Keeala

At level 89-90 wc i got 50-53k an hour from willows at Barbarian Outpost and 59-63k an hour from teak in Kharazi Jungle (dropping the teak logs). This was when i was alone at both spots. I haven't checked the exp from the rest.

I'm sure there are other ways of getting one, but the one i know of is a respawn on the second floor in Ardougne castle. 61 thieving (i think) is required to picklock the door to get to it.

I got both my large and huge pouch before i had 50 runecrafting, so that can't be the reason it's not dropping.