Here are Australian (and Australia-available) pet food companies that explicitly offer grain‑free / “no wheat, no corn” formulas or advertise avoiding fillers. I’ve put a short note and the brand source for each so you can check specific products.

• Black Hawk (Australian) — offers a Grain Free range (states “0% grains… No wheat, corn, barley or rice”). (blackhawkpetcare.com.au)
• Ivory Coat (Australian) — markets grain‑free lines and states “NO added wheat, corn, rice or soy.” (ivorycoat.com.au)
• Meals for Mutts (MfM) (Australian) — promotes grain‑free/gluten‑free formulas and says “No Fillers / free from wheat, corn …” on product/FAQ pages. (mealsformutts.com.au)
• Pure Life (Australian) — sells a Grain‑Free range and states “No fillers… Grain free & allergy friendly.” (purelifepetfoods.com.au)
• Tucker Tub / Petz Tucka (Australian fresh/raw brands) — make fresh/raw meals with “no fillers, preservatives or additives.” (tuckertub.com.au)
• K9 Natural (New Zealand, widely sold in Australia) — high‑meat freeze‑dried / canned diets that state “No grains… No fillers.” (au.k9natural.com)
• ZIWI Peak (New Zealand, widely sold in Australia) — air‑dried and canned “grain‑free” recipes and says its recipes are free from grains/fillers. (ziwipets.com)
• Champion Petfoods (ORIJEN / ACANA, sold in Australia) — the company highlights recipes without wheat/corn/soy and many ORIJEN/ACANA formulas are grain‑free (note: they also offer some grain‑inclusive lines, so check individual formulas). (championpetfoods.com)

Quick notes:

• “Grain‑free” and “no wheat/corn” are product‑level claims — some brands sell both grain‑free and grain‑inclusive formulas, so always check the specific product ingredient list. (championpetfoods.com)
• If you’re changing your pet’s diet because of suspected allergies or sensitivities, it’s best to discuss with your vet (they may recommend an elimination trial or a vet‑formulated diet).

If you want, I can: (a) pull up grain‑free product pages from any one of these brands, (b) compare ingredient lists for two specific formulas, or (c) show nearby Australian retailers that stock them.