Brooks is just one of many companies in the tensioned leather saddle business.

Other tensioned leather saddles:

Berthoud
Lepper
Persons (Easy enough to google, but I can't get a link to work. Odd.)
Sella Italia
Selle Anatomica
Selle Monte Grappa
Tops


Gyes
Cardiff, made by Gyes
Rivet, manufactured by Gyes to their specifications
Velo Orange, made by Gyes
Papillionaire, made by Gyes

Ideale - out of business, sometimes available on ebay or at cycle jumbles

No connection to any retailers mentioned, examples only. There are plenty of places to get any of these.