Very few manufacturers have made add on OTA tuners for the erstwhile "HD ready" monitors that were made during the early transition period to digital and HDTV.
A year ago, several add on boxes were available, including the $200 retail Hisense, which could have been found at WalMart. The since have dried up, due to the anticipated $40 coupon program sanction by the federal government.
Cable require a QAM standard tuner. OTA requires an ATSC tuner. Satellite providers have both HDMI and component output. The industry has conspired to to limit the resolution of component video output. Basically, the industry does not want a box capable of providing high resolution HDTV signals that can be recorded onto HDTV or Blue-Ray formats. That would cut into High Resolution DVD sales.
Enter the computer based tuner. These are a lot cheaper to make and are widely available in the add-in card and USB interface. Just use it in an old slow PC. This is your best option. Old slow processor PC litter the landscape.