Not complicated at all if you have the money. You can shop ebay.
https://www.ebay.com/itm/1-Kw-NEW-Br...AOSwj0NUmEu L
Not sure what the laws are where you are but in the US, they are a bit strict.
But here there is a clause here that allows you to transmit just about anything if they are under 1 watt and the antenna is under 1 meter in length and is directly connected to the transmitter as a one piece device. Then a assurance that you cause no harmful interference to any licensed service.
If you are clever enough, for short range stuff, you can probably hack what you need from existing devices. But there use to be some small transmitters on ebay under $500 but they are not 'clean' enough to be amplified without a bandpass filtering.
Funny I can't find them listed using the old search terms since ebay has screwed everything up.
One other way for short range is to use a Blonder Tongue agile processor and make a matching unit for a antenna as they were intended for cctv..
here is one more example of something you can hack into service
https://www.ebay.com/itm/Original-Sa...AOSwfbhbyTW 9.
Good Luck !