It depends on where you are.
Ebay, your local Craigslist, maybe a local BestBuy, not sure if they pulled them when 10.6 came out. Amazon has them, but they are used and expensive.
If you can wait a week or two, there will most likely be a SL method for non Mac owners to follow.
Mini 9 | OS X 10.6.7 | NBI 20100616212351| BIOS 05 | 32 GB Runcore | 2 GIGS RAM
10V | OS X 10.6.7 | NBI 20100616212351 |BIOS 06|160 GB|1 GIG RAM| 6 Cell Dell Battery
Back up Mini 9| OS X 10.6.7| NBI 20100616212351| BIOS 05 | 32 GB SuperTalent | 2 GIGS RAM