On which Cisco device is netflow supported?

NetFlow is most likely available in any devices on the network.

Device	Supported
Cisco 800, 1700, 2600	Yes
Cisco 1800, 2800, 3800	Yes
Cisco 4500	Yes
Cisco 6500	Yes
Cisco 7200, 7300, 7500	Yes
Cisco 7600	Yes
Cisco 10000, 12000, CRS-1	Yes
Cisco 2900, 3500, 3660, 3750	No
Cisco ASA	No (*)

(*) Cisco ASA supports NetFlow version 9, but a packet field is not exported and CFI is not accepting flows without it.

As alternative you can use FlowMon probes. The probe sniff all traffic going through the line. The main advantage of probe is its ability to analyze every packet at wire-speed up to 10 Gbps, it is L2/L3 invisible and can be connected to any point of your network. The probe can be connected to the user network in three ways: via mirrored port (SPAN); via Ethernet splitter (TAP); or via built-in splitter. See the following URL http://www.caligare.com/product/flowmon/ for more information about probes.