Are you referring to the Australian Jaycar store? I know the Australian Jaycar store has their two highest value inductors with ferromagnetic cores. The lower value inductors are air cored. One idea that came to mind, is if the air cored inductors had a large enough hollow to fit on the ferromagnetic bar. That might get a bit costly. If you have a Dick Smith store near you that carries parts, it might be cheaper to buy the ferromagnetic bar from them, and buy the air cored coils from Jaycar. That is, if the ferromagnetic core is suitably sized to fit the air core inductors and wide enough to cover the width of both of them. It is all relative, but still a little costly in my eyes. It is a bit time consuming in that you need to find the dimensions and may be more practical to go into the store to see weather the idea is practical or not.
That is one idea, but i would really need to see a circuit. Can you provide a link to a schematic/ circuit that you have been contemplating.
That is one idea, but i would really need to see a circuit. Can you provide a link to a schematic/ circuit that you have been contemplating.