1SaleADay via eBay offers the Vivitar Digital Slave DSLR Camera Flash, model no. SF-3000, for $12.99 with free shipping. (B&H Photo-Video charges a buck more.) That's the lowest total price we could find by $2; several stores charge beyond $20. This slave flash can be used with any digital camera and mounts to the hot shoe. It features an auto pre-flash sensor, three power levels, and an 8-second recycle time.