I hit a similar problem with the Pixie2 I made previously. I don't have access to any of the named toroids that you find in the HAM radio journals and books. You know, names like T37-6. So I'm doing the numbers to try to lash up a air-space coil instead.
I'm reproducing the 30m QRSS Receiver as built by Hans Summers, G0UPL. Its a hardware defined radio that outouts audio to a peecee to decode.
I have a handful of plastic coil formers that appear to be 1/4" x 1". They have a fiber board on the bottom with five terminals to connect you inductor elements to and your pcb.
So using the calculator at kitsandparts I worked out that following table;
So I've spent half the day crunching the numbers to work out how to get an air-spaced to get the numbers to match the above... The numbers just don't work =/ I'm sure I'll find something and maybe I'll just have to put a bunch of cash aside and make an order to the US.