You could try this site:
Conexant makes cheap chipsets which are built into a lot of modems (including softmodems) with different brand-names.
There is now another company Linuxant which produces Linux drivers in different Linux flavours for the various modems which are built on Conexant chipsets :
http://www.linuxant.com/drivers/
This website will identify if you have a Conexant chipset modem and supply a free basic driver (limited to 14kbps data - try this one first for compatibility) or a paid-for driver ($14.95 for 56kbps with fax). It is unusual for my modem connexion to get more than 3 to 5 kbps anyway and I think this is not rare.