Not yet, no.

Current state of the art accessible to a customer is way off from that. Exoskeletons are maybe ten to fifteen years out from being something that’s going to be really ready for prime time, as an optimistic guesstimate. But that won’t be personal gear unless you’re very wealthy.

Honestly, because of how much demand there will be in industrial settings, I don’t expect it to reach a level where the average person can just run out and buy one in any of our lifetimes. Maybe a generation after that? Two? But it is possible that it will within that time frame, but I expect they’ll be absurdly expensive if so. Like high end sports car expensive, if you want them to be worth a damn.

Besides, the spare arm idea is limited in use, as others have said, by the ergonomics of it. A robot arm still needs to be securely attached to you, and the rest of your body has to compensate for the weight and motion. Even with super light materials, you won’t get them lighter than your meat arm unless you want them weak