Hi,
as already mentioned, it's sysid is encoded from router-id, you can try either
show isis database 1280.4916.9054 extensive | match "IP router id"
IP router id: 128.49.169.54
show isis database R2_re extensive | match "IP router id"
IP router id: 128.49.169.54
the second one looks more convinient you just need a hostname, hope that helps