For the price of a corvalus it's unlikely you'll find a cost effective replacement. That sucks imo and I hope you find something. Maybe coating it when new with lanocote or something will help.

Might be overkill. I have this one if your interested.

Agree with cirrus, have owned 2, handles were all good, no corrosion at all. You can get the "power handle" for them. You may have gotten that 1 in a 1000. Mine were older though some 12yrs ago, maybe material changed since then. Anywhoo other options for reels to look at if wanting to stay with overheads... Penn fathom 12 or 15 great reels have owned 3, 1 is a lever drag, great reels. have 2 left. Daiwa Lexa with power handle, upgrade drag when it wears out, fathoms drags well there Penn. drags washers are great... these reels are twice the price of a Corvalus though. If you bought it from a tackle store try them for replacement handle. You'll notice not one of those reels I mention are shiman.....  

Thanks for all the advice and to Crochet Cast for the handle option. After trying the overhead reel with the corvalus I think I prefer the spinning reel so I think I'll just cut my losses.