The closest I came to your model # was 42587x50B. Likely has the same Peerless VST205 transaxle, but you want to verify to be sure. Peerless doesn't exactly exist as it did when your tractor was made. Below is a link for one on Ebay, though you may find another source. If you decide to go ahead and order it- you may want to double check that the wheels will come off the old one first.

Here is a link that might be useful: ebay