Need advice on replacing console mounted fishfinder

http://i123.photobucket.com/albums/o...1974/photo.jpg

Here is a pic of my problem. I just purchased a "new" 1997 hydrasports bass boat. There is a recessed portion in the dash for this nonfunctioning lowrance to fit just perfect. I assume it came this way from the manufacturer. I would like to replace this with something that actually works. The dimensions of the hole is exactly 5" x 5". As you can probably see I can't make the hole any larger.

Any ideas?

Check the specs on some of the DF by HB and Lowrance. Some of the small screen ones (3.5") may fit it the hole. My friend has a 97 Stratos with the same setup. I think it still has the original unit in it, but it is a GPS combo and it still works.
SeaRay

Thanks SeaRay, that might just work...I just dont know how to "fill" in the extra space if I find a fishfinder that is smaller than 5 x 5.

Check out the NAVMAN units that come on the newer Lowe boats. My cousin bought a 2007 Lowe that has one that looks to be the same size.