@Dave McLaughlin - Let me see if I understand the Architecture:
Fingerprint device is attached via ethernet.
You want the device to be attached via WIFI.
You need to convert the fingerprint device's data from one format to another.
If I understand correctly, then you could use a WIFI to ethernet bridge to put the data on the wifi network, then have "something" convert the fingerprint data that is broadcast into the MQTT that you desire.