You can now buy a Fuji X-T4 Extended Spectrum (ES) infrared camera directly from B&H Photo. As FujiAddict already noted, you will have to first qualify before purchasing the camera - see the details in the linked document ("CONFIDENTIAL DOCUMENT"):
"The text sounds like it should be pretty easy to qualify for this camera if you want one for the production of artistic work. These cameras are generally not listed for very long and the confidential document expiring at the end of the year might be an indication of how long the Fujifilm X-T4 Extended Spectrum Infrared Digital Camera will be available." (FujiAddict)
Lifepixel also offers infrared or other camera conversions. They also sell already converted cameras. You can read about the different types of conversions here.
More on infrared photography;
Hawaiian infrared time-lapse of haunting Mamane trees made with IR-converted Nikon D5200 camera
