Also, according to documentation, the source vpn instance should be possible.
source { [ vpn-instance vpn-instance-name ] source-ip-address | interface-type interface-number }
The source address or source interface is configured for the tunnel interface.
But in the parameters prompted for source command there is no vpn-intance option.
[Router1]display this
#
interface Tunnel0
ip address 172.16.1.1 255.255.255.0
tunnel-protocol gre p2mp
nhrp enable
nhrp entry multicast dynamic
[Router1]source ?
X.X.X.X IP address
Eth-Trunk Ethernet-Trunk interface
GigabitEthernet GigabitEthernet interface
LoopBack LoopBack interface
[Router1]