I have purchased quite a few items from Roll Models, and have always gotten good service.
Now, just because they have something listed, doesn't mean they have it in stock, I suspect a phone call would be all that is needed to verify.
If you do use them, and place an order online, you will get an email stating it will be 2-4 weeks before your order is ready to be shipped, I have never had to wait that long, in fact most of the orders I've placed were delivered in less than 2 weeks.
I think that on rarer or less popular items they order them from the distributor as orders are placed, and the 2-4 weeks is a cushion.