That sounds as if you have an Eaton Model 7 hydrostatic unit with a Peerless 1327 final drive unit. Now that I read your first post more carefully, I guess you said that. The Model 7 uses standard hydraulic oil, or in a pinch, SAE20 oil, as I said in the previous post. You said you also need to service the Peerless 1327. You can get a free download of the service manual here:
http://www.wfmfiles.com/download/Tecumseh-Peerless_Motion_Drive_System_-_Transmissions_&_Differentials%28691218%29.pdf
If you refer to Page 8, the lubrication chart, it says all Peerless transmissions that use oil use the same lubricant, SAE EP90, which is about as common a hypoid rear axle lubricant as you can get, so it is as close as your nearest speed shop. The quantity required for the 1327 is 710 ml.
I understand you want to finish your mowing job, which is easily accomplished by topping up the systems with the specified lubricant, but after that is done, you should fix the leaks and change the fluid in the hydro unit. It is a light-duty unit, which is very prone to overheating its oil. When that happens the lubricating properties are permanently compromised, and the fluid needs to be changed.
