PIP No More
Sorry, but I'm afraid you're out of luck. Virtually all TV manufacturers have abandoned two-tuner PIP because the vast majority of consumers get their TV via cable or satellite, not over the air. Also, many cable and satellite boxes offer two-tuner PIP, making this feature completely unnecessary in the TV for most viewers.
Some TVs provide PIP capabilities with their internal tuner and an external source, such as a cable or satellite box or Blu-ray player. Last time I checked, these included sets from Samsung, Sony, and Vizio. Manufacturers that offer no PIP capabilities at all include Panasonic, LG, and Sharp.
If you have an A/V question, please send it to firstname.lastname@example.org.