Me being the cheap bassturd that I am .. I would just use any motor oil .. don't put it on too heavy though .. there have been MANY bikes brought into dealers because .. "Its fouls plugs all the time! .. it didn't use to"
They soaked the filter with oil .. and it cuts off the air ..
.. just put some on and squeeze the filter to spread the oil around .. there shouldn't be any dripping or puddling of oil .. it should be wetted .. not soaked.