There used to be a thing called Waterwitch in the NSA ANT catalog. Would that help?
For those who have not seen it before, Waterwitch is on page 43 of the 2013 catalog here [1], and is described as "Hand held finishing tool used for geolocating targeted handsets in the field". It did seem to require, if I'm reading right, that the target be connected to a malicious GSM router called "Typhon" (page 42).
[1] https://www.cryptomuseum.com/covert/bugs/nsaant/files/NSA_AN...