Not sure on the availability (I know nothing about GPUs) but for this quantity and price you can't just send them money and hope for the best.
You need to use a supplier that can use L/C (letter of credit), even if the amount is relative small and it's trouble to set it up with your bank. You should also visit them, or have somebody to do that for you. Speak to several suppliers and be prepared to stay a few days in China to meet a few of them to make your time worthwhile.
It wouldn't be the first and last time somebody pays and they never ship anything, or they ship something else.
We have been doing this for over a decade, but last time we got burned was not even a year ago. Ordered a few thousand SD cards for a device that boots Linux on power up from a new supplier. When we got the shipment, only the first layer on top was good, all the other cards are clearly RMAs (scratches, markings, etc). The guy who took care of the order was only working for the company for a few weeks and my colleague was too stressed to properly monitor him. We are using more expensive and branded SD cards now, which we can get locally. If I would have been aware of this order I could have told them up front this will not end well
Also, don't trust their shipping dates. I've a lot of items on order from who I believe is the factory. First they had stock and promised 10 days. Then some component was missing and hence it takes longer to manufacture. When I requested bulk packing (ie. I don't need them to pack them one by one, I don't even need the retail packing) they said impossible because goods already in stock. Which one is it? Take home message (at least for cheaper items that you need in larger quantities anyway): place orders with multiple factories, they all sell the same crap anyway. If they say 1 months, it will take 2. Be careful even with repeat orders, unless you know the factory very well.
Be very careful with China in general, especially if you have no experience ordering directly. The people who order directly from China successfully go through many extra steps and I am almost certain they had to learn their lesson or two when they started out. Everyone on Alibaba will claim they have stock and they are the manufacturer. It's one of the worst sites, always has been.
I am in Hong Kong by the way.