GSM,Wlan,GPS,LTE &bluetooth jammer
Despite working based on basic physical principles, these are sophisticated electronic devices. Without prior knowledge in microelectronics and experience in building custom HW you don't stand a serious chance to build one yourself. These devices used to be easy to purchase online, I remember dozens of offers on AliExpress, but their use was always considered highly suspicious at best or outright illegal in most jurisdictions and they're not offered on Ali anymore.
Your best chance is to search chinese marketplaces and telegram channels, maybe hit up a seller or two who list GSM device finders and ask them for a jammer, but you better take extra caution for shipping and ship to a fake name so that the customs don't come knocking on your door to ask why you're importing a device that has no legal use unless you are an expert in the field who can demonstrate their very specific use case within the bounds of the law.
Your best chance is to search chinese marketplaces and telegram channels, maybe hit up a seller or two who list GSM device finders and ask them for a jammer, but you better take extra caution for shipping and ship to a fake name so that the customs don't come knocking on your door to ask why you're importing a device that has no legal use unless you are an expert in the field who can demonstrate their very specific use case within the bounds of the law.