If your shop is open to teh public, I'd buy a policy.
If it isn't....or its a hobby, then your homeowner's policy will protect you.
I'm in the insurance business, but I'd recommend not spending the money.
Talk it over with your homeowner's agent to be sure. they won't sell you something unnecessary unless they're a crooked agent...and if they're crooked, you ought not to be doing business with them anyway.
Now don't tell them about your doberman, rottweiller, or pit bull puppy when you call- you might get canceled.