Sequential UUID Generation

Hi,

We have migrated from Oracle to Postgres, there because of the replication
requirements we used UUID columns.
I did a POC(in postgres) with sequential UUID against Non sequential which
has shown lot of different in space utilization and index size. Sql server
has "newsequentialid" which generates sequential UUID. I need similar
functionality here.
I want to create a function which generates a sequential UUIDs, Any
suggestions or support would be much appreciated.

Thanks,
Uday