Under the stairs, in a closet, like Tranny Potter, or in a chest, under locks, like The Gimp, etc.
900 pounds isn't too much for a pick-up truck like their Silverado,
since the maximum payload is around 1900 pounds.
I'd say the real issue is the volume. I'm not an expert on the relative density of wool, but DuckDuckgo gave me a neat
calculator tool.
For our purposes, let's assume alpaca wool is just like regular old sheep wool in terms of relative density, so that means it weighs 0.04 tonnes - 88.3 pounds, let's just round it up to 90 - per cubic feet, bringing us to a bit over ten cubic feet for 900 pounds.
Never mind, according to this
spec sheet, the cargo capacity is 53-61 cubic feet, so they're safe there as well. Their personal luggage won't take up much space either, so fuel is going to be the biggest expense.