How can I replace the nmblookup command on Lion?
Did you have a look at the man page?  

Shouldn't smbutil lookup [-w host] name do the job?


 Global options are as follows:
 -h      Print a short help message.
 -v      Verbose output.
 The commands and local options are:
 help command
         Print usage information about command.
 lookup [-w host] [-t node_type] [-e] name
         Resolve the given name to an IP address.  The NetBIOS name server can be directly specified via
         the -w option. The NetBIOS name type can be specified via the -t, the default is to lookup file
         servers. For a complete list of name type please see "http://support.microsoft.com/kb/163409".
         The NetBIOS names will be unpercent escaped out if the -e option is specified.
 status [-ae] hostname
         Resolve given hostname (IP address or DNS name) to NetBIOS workgroup and system name. All Net-
         BIOS names will be displayed if the -a option is specified. All NetBIOS names will be percent
         escaped out if the -e option is specified.



For me this worked (replacing your example):  

smbutil lookup -w 172.16.0.10 -e domainPC | awk '/IP address of/ {print $5}'