Twinax is very old technology, so its better to get a tcp/ip solution. You can find several IBM compatible thin clients that will work with more functionality that a console. BOSaNOVA is one company you can look into.
use the IBM supplied Operations Console. You can configure it to use an IP address.
If the console will be fairly close to the system, one cheap and easy answer is a Windows PC running OPS Console on a serial port. We even have one like this which also allows remote access through MSTSC.