That's a nice solid cabinet, which for $130 (posted) is a decent price for it.
The Bunnings first aid cabinets are lighter duty (you may need to set a location on the Bunnings crappy site for the links to work)
$39 for 310 x 360 x 100mm
http://www.bunnings.com.au/products_product_sandleford-310-x-360-x-100mm-first-aid-box_P6100189.aspx?search=first+aid+cabinet&searchType=any&searchSubType=products
$59 for 310 x 450 x 150mm
http://www.bunnings.com.au/products_product_sandleford-310-x-450-x-150mm-first-aid-box_P6101363.aspx?search=first+aid+cabinet&searchType=any&searchSubType=products
Otherwise someone posted this one on ebay $53 (posted), 300 x 300 x 120mm
http://www.ebay.com.au/itm/FIRST-AID-MEDICAL-CABINET-KIT-BOX-STEEL-LOCK-AND-KEY-SOLID-POWDER-COATED-/300920471240?pt=AU_Medical_Special_Needs&hash=item461041fec8
The Bunnings first aid cabinets are lighter duty (you may need to set a location on the Bunnings crappy site for the links to work)
$39 for 310 x 360 x 100mm
http://www.bunnings.com.au/products_product_sandleford-310-x-360-x-100mm-first-aid-box_P6100189.aspx?search=first+aid+cabinet&searchType=any&searchSubType=products
$59 for 310 x 450 x 150mm
http://www.bunnings.com.au/products_product_sandleford-310-x-450-x-150mm-first-aid-box_P6101363.aspx?search=first+aid+cabinet&searchType=any&searchSubType=products
Otherwise someone posted this one on ebay $53 (posted), 300 x 300 x 120mm
http://www.ebay.com.au/itm/FIRST-AID-MEDICAL-CABINET-KIT-BOX-STEEL-LOCK-AND-KEY-SOLID-POWDER-COATED-/300920471240?pt=AU_Medical_Special_Needs&hash=item461041fec8