I have an OEM copy which I bought at computer suppliers where I have a trade account. Not sure where your coming from though about the activation thing. OEM's that are bought, ie other than those supplied with machines by Dell HP etc still require activation. So basically, short of buying a new machine you will not get a legal OEM that doesnt require activation.
If you're desperate for an OEM copy, i quick google shows that Overcclockers UK has OEM versions for sale, but be aware that if you purchase and return it opened, they will probably not refund it, as it will be unsaleable, especially being OEM.
Another word of warning, if you need to contact M$ for tech support on any aspect of the software it will be chargeable due to you having an OEM version of their OS, either that or be directed back to the source of your purchase. They dont give free tech support basically on OEM, and they ask for the number displayed when you do a System Properties which states its OEM.