Interesting. I'll have to have a look into them.It looks like Hectic Valley Poultry in Qld, Sarah's Hobby Farm in Canberra, Scratch & Hatch Poultry in Sa and Rob's in NSW are also listing buff Sussex for sale.
https://eggsellent.com.au/poultry-breeder/queensland/hectic-valley-poultry/
https://eggsellent.com.au/offers/act/fertile-buff-sussex/
https://eggsellent.com.au/poultry-breeder/south-australia/scratch-hatch-poultry/
https://eggsellent.com.au/poultry-breeder/new-south-wales/robs-brahmas-australoops-buff-sussex/
It seems a few of them on eggsellent don't know the difference between a buff Sussex and a Quamby though, so you would want a photo of the roo or to see the roo in person before you bought eggs off any of them.
Quality is super important to me. I did get buff Sussex out crosses last year and I still have 3 hens from that I'm planning to get rid of soon. They're probably part Quamby. Carry yellow skin and there was no way I'm breeding that into my line.