/* Extended Gateway Data */
/* opaque = flow_data; enterprise = 0; format = 1003 */

struct extended_gateway {
   next_hop nexthop;           /* Address of the border router that should
                                  be used for the destination network */
   unsigned int as;            /* Autonomous system number of router */
   unsigned int src_as;        /* Autonomous system number of source */
   unsigned int src_peer_as;   /* Autonomous system number of source peer */
   as_path_type dst_as_path<>; /* Autonomous system path to the destination */
   unsigned int communities<>; /* Communities associated with this route */
   unsigned int localpref;     /* LocalPref associated with this route */
}

Arista EOS supports aspath if you enable sflow extension bgp. Cisco also claims to support the feature on IOS XR platforms.

In addition to BGP, there are a number of MPLS, tunnel encap/decap etc. sFlow extended structures. 

Also optical interface metrics, dropped packet notifications, and more:

https://sflow.org/developers/specifications.php