Amazon.com: SABRENT 4-Port USB 3.0 Hub for iMac Slim Uni-Body (HB-IMCU) : Everything Else
Rybozen 3.0 Multi-Card Reader, 6-in-1 USB 3.0 Hub with 3 High-Speed Ports,
1 TB SSD - iFixit Store
USB 3.0 for iMac mid 2011 | MacRumors Forums
USB 3.0 for iMac mid 2011 | MacRumors Forums
Apple iMac 21.5" - Spring 2011 Reviews, Pros and Cons | TechSpot
SABRENT Premium 4 Port Aluminum USB 3.0 Hub (30" Cable) for iMac, MacBook, MacBook Pro, MacBook Air, Mac Mini, or Any PC [Silver] (HB-MAC3) : Everything Else
USB 3.0 for iMac mid 2011 | MacRumors Forums
USB 3 + Wifi ac + BT4.2 for iMac 27" mid 2010 | MacRumors Forums
Refurbished: Apple iMac Mid 2011 21.5" A1311 Sierra i5 2.5GHz 8GB DDR3 500GB ATI 6750 - Newegg.com
USB 3 + Wifi ac + BT4.2 for iMac 27" mid 2010 | MacRumors Forums
4-Port USB 3.0 Hub For iMac - Sabrent
Adding USB3.0 to late 2009 iMac (11,1) | MacRumors Forums
SSD upgrade for iMac mid 2011
Amazon.com: SABRENT Premium 3 Port Aluminum USB 3.0 Hub with Multi-in-1 Card Reader (12" Cable) for iMac, All MacBooks, Mac Mini, or Any PC (HB-MACR) : Everything Else