you guys.
I bought a buckling spring keyboard for under $50 shipped recently and it is tenkeyless. It's a model F even.
Behold the mighty Model C1 (3178) keyboard. If you notice, on some versions, the tenkey is covered up. Mine is the data-entry layout, and so of course the tenkey is gone.

(photo credit to sandy55!)
Also note: that tenkey area can be a phone style, tenkey style, extra PF keys or nothing depending on the model.
Here are the four types (out of the manual)

(C1 (data entry) has no tenkey)

(C2 has extra PF keys)

(C3 has a tenkey with extra PF keys)

(C4 has PF on the number row and extra PF on the tenkey) (I want this one for the cool numberrow)
Anyway, it's not currently usable with a modern computer, so you might not want it, and while it's tenkeyless, it's not actually shorter. It's up to you if you want one, but tenkeyless keyboards are popular, TKL buckling spring boards are rare and much sought after.
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Now another TKL buckling spring keyboard is the "unsaver". It is about 0.25" shorter than a standard model M, so it doesn't save much space, but it's a lot less than the infamous 122-key terminal keyboards. These are vanishingly rare, and almost never found at this price, but the part number for the PS2 one is 1387033 Here's a picture (courtesy of epiguru)

After that, there's the kishsavers, which are (if possible) even more rare, and have metal cases. Good luck finding one at any price.
(picture credit: kishy)

That's a quick rundown on some tenkeyless buckling springs!