CMS 512MB (1X512MB) DDR1 2100 266MHZ ECC Registered DIMM Memory Ram Upgrade Compatible with Cisco® 2811 Router Main Memory DMemory Ram Upgrade2811-512D for Server Only - C89 at Amazon.com
Amazon.com: MEM2811-512D 512MB DRAM Memory And MEM2800-128CF for Cisco Router 2811 (PARTS-QUICK BRAND)
Cisco Approved DRAM Memory MEM2811-512D 512MB for Cisco 2800 Series 2811 | eBay
MEM2811-512D= 512MB Memory Cisco 2811 Router DRAM (#140597813999)
CISCO MEM2811-512D MEM2851-512D 512MB DRAM MAIN MEMORY FOR CISCO 2811 2821 2851 | eBay