I have heard of people using other oils, but I have also heard the line that one should use nothing but the genuine oil. I, myself, err on the side of caution with my LP12.
You might be able to get the oil from Linn--the best way might be to call them, since it's harder to ignore a phone call.
Otherwise, you might find a Linn dealer who's willing to do mail order.
One final thought--you might think about replacing the oil that's already there. That is, drain the bearing, and refill it. Often, you'll hear that you "only need to top off." But, from my experience with the LP12, I think a complete oil change isn't a bad thing from time to time.
Good luck!