Yes, parts are available, but for the main parts of the pump they are pricey. Cub Cadet wants nearly $400 for the shaft..... but it's available. If you know of a hydraulic supplier, they may be able to get it cheaper. It's just a Sundstrand hydro unit. It's not CC specific. Your best bet is to just buy another unit. You can get a used one for around $75-$150 depending on where you look.
EDIT: Here you go:
http://www.ebay.com/itm/CUB-CADET-10...item35eb27161e