FMP Server 11 Advanced

So, I have been using FileMaker since the day it came out in the 1980s and was produced by Deneba.  we are a small law firm and are currently using FileMaker Pro 11 on about eight or nine clients in the office and FileMaker Pro server 11 in the office. Not one crash in about seven or eight years. However now because of our VPN issues it looked like we were going to have to upgrade all of our FileMaker system but then I decided to try the IW P, putting the database on the Internet. However after a lot of checking and googling it appears that while FileMaker Pro 11, FileMaker Pro 11 advanced, FileMaker Pro server 11 advanced cane each published to the website that FileMaker Pro server 11 cannot. So the question is where can I purchase a copy of FileMaker Pro server 11 advanced? Anyone have any suggestions? I don't want to upgrade the entire office to the next levels because everything is simply working beautifully. Thanks for any information you can provide.    [email protected]