well thank you but really??? I guess I had thougt the SVS cylinder type units were really revered in the forums as being something special, am I wrong??
Subs were fairly new back then. Sub drivers have improved in leaps and bounds since then.
Your next problem is that if you are using two subs they need to be identical or close.
If you can't find that sub used, then we will have to know the specs very precisely and find a driver that with the right enclosure will match your current sub.
In terms of work and effort, it would be a lot easier to buy or build two new subs.
So if after a period of time looking on eBay and Audiogon you don't get lucky, then your options are:-
Stick with the one sub you have.
Have someone design a sub that will be a very close match, and you build it or engage someone to build it.
Buy two new subs.
Build two new subs.
I personally would advise one of the last two, if you fail to find another sub like you have, and feel you have to have two subs.
You don't have any other options that will be better than what you have now, other than the ones I have given you. You may not like it, but that's the way it is.