I have a player that created an R2 unit for his PC and is pretty much a non-combatant, but still needs something for some kind of defense if absolutely necessary. Looking at the astromech droid in the adversary chapter, they have an arc welder that does 3 damage. Looking through the equipment chapter, I couldn't find this item. Am I overlooking it somewhere? I just told him it would cost 100 creds.

Also, would this cost more to install on his body, or would it be assumed that it is attached already? Thanks for any input!

Not sure of the cost, would like to know myself, but the latter question I can answer. Whatever the cost it would be the same for organic and droid alike. Droid characters can say whether something is attached or not, but encumberance still applies as per normal.

An arc wielder is a basic tool that should be included in the basic tool kit, p.181-182. For some reason they call it a "laser wielder" in the description, but I never remember anyone using a "laser wielder" in Star Wars.

Either way, as an R2 unit, he should want to have a tool kit installed for a multitude of reasons. So if he already has the tool kit installed, I wouldn't make him pay extra for the arc wielder.

For the R2 Technician/Mechanic that a friend of mine wanted to play, I just included the arc welder as being part of the tool kit that seems to have as standard built-in equipment for astromechs, using the Melee skill to determine his attack dice pool.

Anything beyond that (such as a circular saw) I had him purchase equivalent weapons. So for the circular saw, we simply used a vibro-knife, labeled it as "built-in" and simply changed the name to "circular saw."

As for buying an arc welder as a separate piece of gear without a tool kit? I'd say 100 credits is a fair cost. It's a third of the cost of a set of stun gloves, but does far less damage (the gloves can do regular damage and stun damage; arc welder just does a fixed amount of stun damage), so it's fair.

The Age of Rebellion Beta has a Fusion Cutter in the equipment section that has stats for using it as a weapon.