My 400 uses a AR26375 and there are plenty available on Ebay and amazon etc, Mine was crushed and needed replaced. I see one on amazon for $24, most are around $32
Is it in good enough shape to put back in? If it's not badly damaged (no holes or crushed) clean it thoroughly and put it back in. The bigger question is what does the sump look like? If it's got a lot of crud in it then it really needs a good cleaning. From my research that has a piston pump. Hopefully it's not trashed it from starving for oil. If it cavitates you can hear it clearly believe me. What does the fluid look like? After the fact and no ever does anything with the fluid until they start having issues and then it may be to late. If it's dark that isn't a good thing. It should be pretty clear and light yellow.