Water-Resistant Treatment for Sheepskin Jackets?

[raf]

Looking for a surface (topical) substance which can be applied to the exterior surface of Sheepskin leather jackets without harming the leather whatsoever. I'm NOT interested in applying any sort of impermeable coating which could crack over time. I also understand that such surface treatments are NOT "Water-Proofing" but "Water-Resistant" at best, and whose effectiveness will diminish over time until re-applied.

Please help.