These people make an oil called 'Premier 90' that is a straight 90 weight gear oil with no EP additives. I don't know if they do mail order but they have depots in St Helens, Newton Abbott and Rhuddlan.

By the way, if you are unsure about any oil you have, take a sniff. If it smells like engine oil it is ok. If it has a pungent sulphurous smell it isn't.