I'm not familiar with the specific Seiki TV model sc55au600. I fired up MyHarmony (Logitech) remote software because I use their Universal Remotes with all of my systems and while it recognized the brand Seiki it did not recognize the model SC-55AU600 as sold in Australia.
https://www.replacementremotes.com/ lists about 15 SEIKI remotes available with pictures so you can see if you recognize one matching your lost or broken one. Also, if you click on an individual unit it shows which TVs it is compatible with. I tried https://www.tvremotes.com.au but found no results for SC-55AU600. I would probably shop it on www.ebay.au which currently lists 85 remotes for SEIKI TVs.
Answers & Comments
I'm not familiar with the specific Seiki TV model sc55au600.
I fired up MyHarmony (Logitech) remote software because I use their Universal Remotes with all of my systems and while it recognized the brand Seiki it did not recognize the model SC-55AU600 as sold in Australia.
https://www.replacementremotes.com/ lists about 15 SEIKI remotes available with pictures so you can see if you recognize one matching your lost or broken one. Also, if you click on an individual unit it shows which TVs it is compatible with. I tried https://www.tvremotes.com.au but found no results for SC-55AU600. I would probably shop it on www.ebay.au which currently lists 85 remotes for SEIKI TVs.