I think if you get a Cisco SOHO 97 and set the internal ip address of your tenor as a visible server it will do the job. CISCO SOHO series are cheap and work well. You can configure the router very easy using the web interface. Do not forget to set the “External IP Address” for your tenor. Just type “unit 1” Press enter and then type “extip YOR_EXT_IP_HERE” and hit enter.
Hope this helps.