There are alternatives for the running lights on the '15+ nismo to make that conversion more affordable (IMO they actually look nicer than the factory ones). You can find that info (and all the rest of the info you need if you want to make this switch) in this gigantic thread:
2015 Nismo Bumper on 2009 Sport possible?
Or just go without them and let it look more 'venty'.
Going with an aftermarket bumper (unless you order a real one directly form Japan) is going to be more expensive as it will be laborious for your body shop to get it properly fit up.