I am looking for a short-wave antenna kit for a magnetic loop antenna.

Do you mean a kit to make a loop antenna for shortwave reception? Or a kit to
add shortwave reception to an already-existing loop? I'm not trying to be
snide, just not exactly sure of what you're looking for. Shortwave loops are
not so readily available in kits or built form unless you can spend a few
hundred dollars to get the full HF range you want. There are, however a NUMBER
of sites online which show how to build a shortwave loop antenna for a LOT less
money than buying, say, the Palomar SW loop and elements... do a search for
shortwave loop antenna project, or something similar.
Ed from Torus Tuner Loops used to make a number of SW loops but recently ran a
post stating he was no longer going to be doing this. His items were great
though, and I got a 3.5 to 18 MHz loop from him which REALLY made a huge
difference on my portable radios, and even my Icom R75 when conditions
warranted my using it.
His prices were great too (MUCH cheaper than any comparable antennas, and in
fact his stuff was very unique if you ask me)...
Best of luck-
Linus