All the tools that you will see local people using can be bought in any local market - sickles, machete, crowbar, wood saw, brooms/sweepers etc
Toko Bangunan have tools like shovels, hoses, etc
You can find the odd item at Hero or Grand Store in Mataram Mall but
For 'western' tools I go to :
Superstore or Depo Jaya in Sweta, Mataram
Superstore is better these days - secateurs, pruning saws, hand trowels, sprinkler systems, hoses and connectors, garden shears ( the expensive metal green ones are by far the best). and lots more. Don't buy the cheap stuff !
Leaf rakes at BJ's behind MGM in Mataram.
Haven't found a spade yet!