Where can you buy preprogrammed atmel microcontrollers such as the attiny13a microcontroller in a surface mount package?
I know you can buy preprogrammed PIC microcontrollers, but not atmel microcontrollers...
You tagged the question production, does that imply large quantities, at least hundreds to thousands per year? If you're a professional you may buy through distribution, and most distris have a programming service for all microcontrollers on their line card.
You have options like a unique code programmed where you want it, and labeling like kapton or lasering. It will cost roughly between 10 and 15 cents, depending on quantities.
I've used programming services from EBV and Spoerle. PCB assembly shops may also offer the service, but I guess they have it done by the distri as well, so you may better go directly there.