Sussex do a similar style to the pic you posted There is a bathroom shop on Victoria Rd in Drummoyne we found to have the best prices for Astra Walker and Sussex.

Not sure where you live but have you tried http://www.architecturaldoorhardware.com.au/ or http://vinco-architectural-hardware.business.site/ ? Ialso foudn some in other places when i searched houzz for knobs - https://www.houzz.com.au/professionals/s/knobs/c/au

I think you are safe with mixing colours if the style is very similar - for example, if they are all angular and look like the same 'family', then it should work. This is a nice example I found online. The door handle actually helps balance the look too. All the best Lauren! Kat website coming soon! download free furniture plan kit here https://mailchi.mp/9c071e61583e/awkwardhome-furnitureplan

hi sorry i cant offer advice - but just wondering who you went through - looking at pivotech products but not sure if they will fail :( thanks