There's probably a sticker on it somewhere with a part number and/or brand name. Presumably if you just search for A/C compressor for 1996 Volvo 850R you'll start to see what's out there. Maybe try RockAuto first, or FCP Euro?
Here's what FCP Euro is showing (note prices in USD):
According to FCP website the original Volvo part number is 8601533...so you can search on that. Looks like this place in US has it on special for $199USD + $18USD flat rate shipping to AUS (seems too good to be true on shipping!)
https://www.coolairparts.com/index.php?route=product/product&product_id=3113
Hope that helps...just be sure it's the correct part before you order! :)