X61, still a great writing/ second machine after all these years : r/ thinkpad
2GB Memory RAM Upgrade for the Lenovo Thinkpad R61 Series T60 Series T61 Series X60 Series and X61 Series Laptops (DDR2-667 PC2-5300 SODIMM) - Walmart.com
2GB (1x2GB) MEMORY RAM 4 IBM Lenovo ThinkPad X61s Series Notebook DDR2 A38 A38 | eBay
2GB Memory RAM Upgrade for the Lenovo Thinkpad R61 Series, T60 Series, T61 Series, X60 Series and X61 Series Laptops (DDR2-667, PC2-5300, SODIMM) at Amazon.com