I'll throw my 2 cents in Tubby...
Keep the bears themselves standard. You can always add more "bears" to the mix. Should make it easier to find a mfg. and keep the unit price down. Sorry I can't help you with a mfg.
Personalize them using clothing or accesories. The "heart" is one idea that could be changed around via velcro. Additional hearts sold separately.
A lot of the time, it's not the "base unit" itself that's the draw, it's all the other "goodies" you can get for it.
Here's a site worth a peek...
Build-A-Bear Workshop-United States: Home Page
Dave