Thanks so much for the informative suggestion. Since there is nothing but the case that remains serviceable and I lack your obvious skill, repair is not practical for me. Since the bell housing seems to be common to several models, I am hoping there is a substitute that will work.
Thank you for the reply. It is a grey market tractor. Some tractors sold in North America are similar but so far I haven't found a source that gives a definitive answer when it comes to starter compatibility.
L1500 is a grey market Kubota 15 HP and parts are still available - also there are a number of discussions over on Orange Tractor too - here's a link to a starter on ebay NEW STARTER MOTOR Fits Kubota/Zennoh L1500 | eBay
As the op is aware, there are "similar" models. It appears that the L1500 is similar to the L175. As mentioned above, there are several results on eBay for the 1500 and 175.
Compare what you have to the photos, and I'm sure you'll find something.