Xiaomi Mi Smart Band 4 US $26.22 (~AU $39.30) Shipped via Xiaomi MC Store @ AliExpress
Price in title inclusive of GST - Don't forget cashback to get it even cheaper.
Thanks to videoman you can use coupon BrandweekP828 US $7 off US $50 Spend Coupon if purchasing two.
NB: One of them would have to be with screen proctector and bonus strap to meet the minimum spend requirement. Total after coupon is AU $73.09