UBI USW-PRO-48-P: Switch, 52-Port, Gigabit Ethernet, SFP+, PoE++ at reichelt elektronik
NETGEAR 52-Port Gigabit Stackable Smart Switch (GS752TSB) - 48 x 1G, Managed, with 6 x 1G/2.5G SFP, Desktop or Rackmount, and Limited Lifetime Protection
Cisco SG300-52 52-Port Gigabit Managed Switch for sale online | eBay