You could use a crystal oscillator, but you'd need a bunch of circuitry to divide the frequency down to 1 Hz. The lowest-frequency crystal I could find is 20kHz. In other words, it's a lot easier to start with 60Hz than 20kHz when you're using individual transistors.
It's not that bad.. typically you use a 32.768kHz ("watch") crystal then divide by 15 to get one second. You can do it with two chips (a bunch of solutions, one is two 7468).
To nit-pick, of course the division is not by 15 (that'd give 2,184.5333... Hz) but by 2 to the power of 15, i.e. 32,768. Typically implemented by a 15-bit counter.
You need 15 triggers to go from 32768 Hz to 1 Hz. Existing circuit uses 4 triggers to divide 60 Hz by 10 and another 3 to divide by 6. You can repurpose those so you only need 8 extra triggers. Two transistors each means 16.
You can also save 6 transistors from existing dividers because all divisions are by 2. So net total is 10 extra transistors for division, plus at least one in the oscillator itself.
