If you are within 40 miles of the broadcast tower and you wish to have reception to show a prospective buyer that the TV is working, I'd suggest to get another antenna. Since you state that you'd much prefer an indoor antenna to an out door one, you could search at Amazon and E Bay for a small antenna that is tuned towards the UHF bands. This can be small in size and fit the bill for what you're after. Heck, a clean piece of wire formed into a 10" circle and run through a balun to the TV may be all that's necessary.
FWIW, I made my own antenna for the RV. I used a design I found on the internet--
Gray-Hoverman array. I had everything at hand except a few aluminum rods. It took an afternoon to build and connect. The picture quality is as good as the plasma TV's in the house with a cable feed.