The Trijicon SRO is a great competitive optic, but yeah, they cost an absurd amount. There are cheaper SRO-like optics that apparently are fine on 9mm pistols so should be ok on a .22. I'm not sure how availability is in Australia but here's what we can get here:

https://www.vectoroptics.com/products/index/sn/Frenzy-Red-Dot.html

The 1x20x28, 1x22x26, and 1x22x32 models specifically. I haven't used these optics but Viridian, a legit company in my neck of the woods, seems confident enough in them to sell the green versions under their brand name.