I will produce one in my garrage for a price. I know good preamps can be bought off the shelf. I'm not sure about the heads, so I'll have to do some research, if I have to make the head cost goes up because I need to buy tools I don't have. Some for the other parts, some I can make already with tools I have, some I can buy quality, others I'll need to charge enough to pay for tools.

I saw an interesting schematic to use a cut off casette-tape head to read the magnetic stripes on credit cards.

I wonder if the reverse could be done-- using the heads that are still (likely) in production for use in card readers, then using some DSP magic to reconstruct a decent audio product?