MS-SQL<->Postgres sync

Looking to keep 2 databases in sync, at least semi-realtime if possible, although running a batch update every x mins wouldn't be out of the question. One db is postgres and the other is ms-sql. It's to keep inventory in sync from 2 seperate locations, one being a brick and mortar store and the other an ecommerce system for a web site. Any and all help is appreciated since I can't find much of anything on syncing these 2 database systems!