(I assume it's IDE, but what rpm?)
http://www.newegg.com/app/viewproduct.asp?description=22-144-122&DEPA=1
80 GB IDE, 7200 RPM 8M cache: Western Digital's "Special Edition"
$75 for a new one, $56.25 for a refurbished one. I wouldn't recommend the refurbished one, but the new one is a great drive (I've bought several).
http://www.newegg.com/app/ViewProduct.asp?submit=property&DEPA=1
A list of all the 80 GB drives they offer, sorted by price. Starts at $69.50 for a WD 7200 RPM with 2MB cache.
http://www.pricewatch.com/1/26/2480-1.htm
Multi-vendor list, starts at $55.48 (after shipping) for a WD 5400 RPM with 2MB cache.