I still watch Ebay for international stuff, which is where I typically find 1950's and older French/Italian parts. I don't do Facebook, but maybe I should for those things.
I've been very disappointed with Ebay's policies on combined shipping. Seller are apparently now being told to ship to the Ebay facility in their country, then that will be forwarded to the international destination. With the way that is done, there is apparently no more control for managing combined shipping. I was interested in some headset races from the UK recently. Shipping 2 races would be about 16GBP. I was curious what the price would be if I bought all 6 sets, for spares, and the shipping jumped to 38GBP. What a ripoff! The extra items would barely affect shipping costs/size. The seller claimed there was nothing he could do and Ebay has employed scare tactics to keep people from shipping outside of their recommended means.