Presale is made by the bitmain site only bro.
You can also use
https://www.antminerdistribution.com aside from bitmain. They've been in business for a long time so they have lots of reviews and also offers reversible payment methods so you're technically safe in case something happens.
I am not sure whether the closed the order or not.
Yes all slots for the current batch of S9's have been taken already (Both in bitmain and in antminer) so you will have to wait for the next batch. Subscribing in their newsletter and keeping up with their social media sites will be helpful.
However you can make the order from the eBay resellers please check the trusted trader who made many sellimgs previously by checking his trade account. If all find place the order with that person. Your amount will be safe.
Only thing to worry is cost will be double the time higher than the value you find in the reselling sites.
Yes you can buy from the usual usual online sites such as ebay and amazon but I won't recommend it as the price is not just double. I just checked it, It ranges from $5K-10K since some are for bidding