Where can I buy a femtocell device

nuclearcat wrote It is distributed only by cellular operators, and it is preprogrammed, as it need to connect to their network. Alfa and touch dont have support of femtocell.
Foreign one wont run, because owner of it, operator, check cell location and they have no permits to operate here.

I agree with your points but also I'd say that "maybe" it is possible to do the complete opposite of what you said.
At the end, not all jamming/spoofing/sniffing devices are purely used by LE and they are obtainable in a way or another.

Jamming/spoofing/sniffing devices sold on public market are very basic RF devices.
Of course you can buy used femtocell, almost all of them are from discontinued services(femtocell didnt proven themself as good solution), so it is just electronic junk, because femto is just radio interface that should be attached to cellular operator infrastructure over SeGW.
Vodafone for example replaced it by wifi calling.
Even if you can find active one, if you are not living in such country - your chances to make it work - very low. If you think about VPN, this device have other means to detect location (and it is not GPS), to not violate operator frequency plan.
Also it might bring you very big troubles, which is better to avoid this days.