You can add the VirtualPrompt command to the device template to specify the custom prompt. The default location for the templates on the NCM server is C:\Program Files\SolarWinds\Orion\NCM\DeviceTypes
from the admin guide:
VirtualPrompt
Specifies the command prompt that will be sent when the device is
ready for command input. Use this command along with the
MenuBased command to specify the exact prompt SolarWinds
NCM should wait to receive before sending commands.