Sadly, the Winegard product line has had several antennas discontinued recently. The YA1713 was one of those items.
Antennacraft still offers the Y10713 and it's a very good option in your case. Given the low signal levels, you'll need to go into the project with the understanding that until you try, you aren't going to be certain of the final results.
If you try a single Y10713 and find marginal results, you still have the option of stacking a second identical antenna. If done correctly, you could net another couple of dB gain out of the combination.
http://forum.tvfool.com/showthread.php?t=1024
Here is a Yagi design calculator if you want to build your own...
http://forum.tvfool.com/showthread.php?t=1106
Consider that is some cases, a tower may be more productive than an antenna or amplifier alone.