Portable Time Sync with Proxy / Firewall setting / recognition

Hello,

it would be nice to synchronize the clock on every computer.
The Windows time service is scriptable, but it does not work with proxies or firewalls blocking port 123.

So is there a small time sync utility without installation with proxy / firewall settings or even recognition?
With (updateable) Time Server list for different countries?
And maybe useable from the command line?

Best regards,
René