Interior Sliding Door Latch or Snib, openable from both sides

Since you're in Aus and I'm in the US, our search results may be a bit different, but I did a simple DuckDuckGo search for "interior sliding door latch".

Scrolling past the "shopping" recommendations (as is my habit), the first result was for Amazon.com listing their "best sellers". Nothing there came up, so I searched for "interior sliding door latch" on Amazon.com. The 1st item listed was a lockable latch. Scrolling down to the "related items", I found this sliding door pull. It's a single item that goes all the way through the door and has a detent on either side.

The second DDG result that I looked at took me to Home Depot listing for a rectangular finger pull. This is a pair of detents that are installed back-to-back in the door so you can pull it from either side.

(IMHO, the single unit would be easier to install since it's one cutout all the way through the door instead of making two depressions, one on either side, and trying to get them to line up. But, we're not here for my opinion...)

You may want to search for either a "sliding door pull" or a "rectangular finger pull" at your local retailer/web-site. If that doesn't work, print out the two images, take it to your local retailer and "point and grunt". ;)

After speaking with a few door specialist stores for doors. I had to settle for buying two privacy sets and latch mechanisim to allow for opening/unlatching on both sides of the sliding door.

(Each specialist was perplexed they did'nt actually have a product to cover this situation.)