Exercise doesn't seem to work well for the sweating as the muscular contraction doesn't allow for good elimination of toxins.
You can purchase a portable infrared sauna from Amazon or eBay for around $200. These work very well. You start sweating within 3-5 minutes.
One couple put up a small tent in their condo, covered it with blankets and hooked up a clothes steamer to it. They would lay inside the tent and sweat. A family in Costa Rica would put on their sweat clothes and winter coats and drive around in the sun with the heat on in their car. In Iraq and Afghanistan, soldiers would dig a hole in the sand and cover it up with blankets, of course, the temperature there was about 135 during the day.
You could put on your sweat suit, cover up with blankets, and sit in front of a heater.