Not so fast. Why are you rebuilding it? If it's leaking, usually it just needs a seal or two, which you can probably get from a bearing or hydraulic house. Or an old time tractor dealer who has been in the business 25 or more years.
If it needs bearings too they are easily found. It's usually only when the actually pump innards are chewed up that you really need genuine factory parts.
I did the pump on my Wagner loader about 20 years ago, was a very easy job (and I knew nothing about hydraulics then), and was still working just fine when I sold the loader.