It's unlikely that you'll find a new set of beaters. The safest and easiest way to remove the rust it to apply a coat of naval jelly, let it soak for a couple of hours, and wash the beaters in hot water to remove it. If the rust coat is heavy, repeat the process. You can use an old tooth brush to remove the rust in hard to reach spots.
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Thankyou for the reply.
I'm sure it is most unlikely I'll find new beaters but do you have any suggestions where I might start trying to find some?
I've never heard of naval jelly - where do you buy it?