Here are a few options.
RCA VT-231, I think the Grey glass tubes are closser to what you want than the black glass.
National Union, I prefer the black glass but think from your post the grey glass again would work for you.
The CBS brown base has a sweet midrange.
The KenRad VT-231 has a nice midrange and very good bass.
The Brimar CV1988 has a nice midrange also.
You can go www.head-fi.org and do a search in the amplification forum for a thread titled
The 6sn7 reference thread
It has about as much info on these tubes (and all 6sn7 tubes) as you will need.
RCA VT-231, I think the Grey glass tubes are closser to what you want than the black glass.
National Union, I prefer the black glass but think from your post the grey glass again would work for you.
The CBS brown base has a sweet midrange.
The KenRad VT-231 has a nice midrange and very good bass.
The Brimar CV1988 has a nice midrange also.
You can go www.head-fi.org and do a search in the amplification forum for a thread titled
The 6sn7 reference thread
It has about as much info on these tubes (and all 6sn7 tubes) as you will need.