Retail Source for Adobe Illustrator 10?

I’m looking for a licensed legal copy of Adobe Illustrator 10 to install on a client’s system but haven’t been able to find a copy at any of our usual software vendors. They all have Illustrator CS but we have to use Illustrator 10 since we’re using custom plug-ins and extensions which are specific to v10.

Does anyone know of any reputable vendors – brick and mortar or online, doesn’t matter which – who are selling Illustrator 10?