It's a Cordon Bleu Blender Liquidiser - you do not help your case by keeping the brand name a secret...
Second hand models are advertised for £10. Buy one and steal the nut from it.
The thread form is very probably metric - nip down to a decent hardware store in your area and buy a few nuts that look as if they might fit - perhaps 10p each.
Ask an old codger who lives nearby and has a small workshop - old codgers just love to help people in difficulty.
Old Codger...
March 2017
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