In a previous post, I described the use of CD-crystals for 17m weak signal operations. This post is attempting to do the same but for the 12m.
The crystals I am mentioning here are also used in CB-rigs, although harder to find. Here's would be a possible source.
QRSS: 37.340MHz => 12.446MHz x 2 = 24.892MHz
QRP/SDR: 37.350MHz => 12.450MHz x 2 = 24.900MHz
WSPR/QRSS: 37.395MHz => 12.465MHz x 2 = 24.930MHz