I'm trying to get a radio clock to sync up with WWVB (60 kHz out of
Colorado). In the place that I want to place the clock, I can not get
it to sync, even at night when the signal is stronger.

Inside the clock is a small ferrite-core loopstick antenna. I figured
out which way the gain pattern pointed on the thing (i.e. not along
the axis of the ferrite rod) and tried positioning the clock for
maximum signal, but no luck.

So now I'd like to try a better antenna. I won't have the time to
make one myself, and I'd probably do it badly anyway. It seems that I
should be able to buy an antenna for this fairly cheaply (thank you to
my capitalist exploiter overlords!), but I can't find one. Ideally,
one designed for WWVB's 60 kHz would be great, but I'll settle for
anything really, as long as it claims to have some decent gain at 60
kHz.

This clock is going inside a building, inside two layers of cinder
block / concrete walls, so it's possible that I just won't be able to
get a signal in there no matter what I use. The
external-antenna-and-a-wire-run concept is the next step, but I'd
rather not to that unless I have to. We're moving out of that
facility in a few months so that would be wasted labor.

What are some sources for loopstick antennas?

On another note, in searching this forum, someone said:

An LF loopstick antenna wound on a 1/2 inch diameter rod is *much*
less efficient than a 1-meter square air loop

Assuming I have the space, am I better off trying this with a few big
loops of wire instead of a small ferrite loopstick? What are the
rules of thumb for comparing the two types of loop antennas?

Thanks!