I would think weapons get handed down generation by generation, same for tent poles etc. Repair spells are the go!
From what I remember the nomads get their wood from the Northern foothills (http://www.glorantha.com/docs/praxian-overview/). Probably once every few years. Spears are made from saplings etc and worked over a fire if not straight.
Pavis would get wood floated down the river and also salvaged from the Big Rubble.
Probably a special tree which grows in sacred areas along the river that provide saplings good for spears. There are certainly ones that provide arrows...