Just a few practical things.
1. Motion sickness is in large part a failure of parts of your brainstem to cope with the fact that movements of your head in space (ie 3 axis) do not correlate with the visually detected movement of your environment. In turbulence, the instruments don't move much relative to your head/eyes even through your inner ear knows that it's being thrown around. Main thing therefore is to keep your eyes as much as possible on something that is not moving in local space (ie the horizon) as your eyes and inner ears will then correlate. Can be difficult in IMC obviously but it may at least be useful to know. This also explains why motion sickness is better eyes closed: there's no discrepancy between eyes and ears.
2. The best vestibular nucleus suppressant (brainstem dizziness centre) is a drug called cinnarazine: however not appropriate unless you're a SLF as it can cause some drowsiness: but may be handy for those days when you are.
cheers