Small Form Factor drives have become the standard for enterprise rack and tower servers. Offering more capacity for drives in a singular chassis than Large Form Factor drives, 2.5" drives have many benefits including, offering more redundancy, better performance due to a smaller disk platter diameter, cheaper price v performance, higher MTBT (mean time between failure), faster random access, lower power consumption and higher IOPS. 2.5" Hard drives have allowed for greater drive density on both 1U and 2U ISS (Industry Standard Servers), turning systems such as your DL360p G8 into a storage server without incurring additional costs in collocation datacentres and additional hardware.
Virtually every brand of 2.5" SFF SAS drive is available at Bargain Hardware, from original HPE 2.5" drives for spare part replacements or storage expansions in HP ProLiant servers from G6 through Gen10 to Dell 2.5" SFF hard drives with hundreds of Dell part numbers in stock at any one time. Dell and NetApp SFF disk drives, compatible with many generations from most manufacturers, are often sold without caddies, caddies are available separately under the caddy section and if bought with a HDD they will be put together prior to shipment.
Whether you need a specific drive as a direct replacement for a failed unit in your SFF server or just need generic increased capacity, Bargain Hardware have thousands of refurbished cheap 2.5” SAS hard drives ready to go.