Apple does not keep a record of owners and there is no procedure whereby you can obtain the contact details of an owner. The exception is if you can find the owner's details on the casing of the iPod or, if it is unlocked, look in the top of the Settings menu and see if there is an email address that you could email with your details.
If the iPod is locked and there are no details on the outer case, the correct thing to do if you found it in:
- the street (road), is hand it in to the nearest police station to where you found it
- a shop, hand it into the shop manager or assistant
- the public part of a shopping mall, you should hand it into the mall's security office
- a train or bus station, public building etc., hand it into the authority in that building or station
- any other building or controlled area, hand it to the authority for that area