I found this website last night while trying to find sources for the specific lubricants recommended by the GRiSO owners manual. I have not ordered form them so don't know anything about their shipping costs but their prices are significantly lower for the gear oil than I saw elsewhere.[You must be registered and logged in to see this link.]
They have the 10w60 for $11.95/ liter and the gear oils (AGIP GEAR SAE 80W 90 and AGIP GEAR MG/S SAE 85W-90) for $7.95/ liter.
I checked their shipping costs. $21.00 USD to ship to CO from TX. I'd have to be buying a LOT of gear oil to make that cost effective.