Are you ready to pay some fee?
For something like 15€/month, you can have a dedicated server else, you can install a ssh server on some computer at home.
In the SSH config file (here for debian : /etc/ssh/ssh_config), configure the listening port to be '80'.
Then at work, use putty on windows, or "ssh" on linux/mac OS to create a tunnel between your work PC and your server.
Make a dynamic tunnel listening on 81
Then with sockscap, make javaw to use this tunnel (socks v5).