Kits are already easy to buy. People don't bother buying the kits because if you use the jammer generally you are found. Occasionally pops up in the news.
" if you use the jammer generally you are found. Occasionally pops up in the news." - only people who are found pop up in the news. Your logic looks faulty.
The thing with phone jammers is that they actively flag "I am here" and are easy to locate.
Because phone jammers cause serious problems to the phone companies, they have teams in the field actively tracking them down. And the phone base stations run software which automatically flag that they are present and log the co-ordinates.