The only thing I can think of that goes that low out of the box is the old Ettus Research USRP1, B100/B110, or E100/E110 SDRs combined with both a LFRX daughter

The only thing I can think of that goes that low out of the box is the old Ettus Research USRP1, B100/B110, or E100/E110 SDRs combined with both a LFRX daughtercard and LFTX daughtercard, which are DC - 30 MHz. The SDRs themselves can occasionally be found on eBay and the daughtercards are still sold directly by Ettus Research or themselves occasionally can be occasionally found on eBay.