That’s an interesting question. Really the only way to protect yourself from electromagnetic radiation is to limit your exposure to it. For example, a sleeve lined with a wire mesh that you can put your cell phone in would block radiation coming from your cell phone, but your phone would also not be able to communicate with cell towers.
I have also seen wire-lined garments such as underpants that claim to block electromagnetic radiation, but the need for such clothing and their efficacy hasn’t been well-established from a medical standpoint.
In short, any small device that claims full-body protection from electromagnetic radiation but does not in fact cover your whole body is likely a hoax.