If you have a friend with an egg-tree in his/her house you can poison and replant. You'll need your friend's help if you're going the fertilidust-lite route since the resulting tree will have 2 eggs (4 harvests).
You don't even need a home with a dark patch. Just find an egg plant in the wild that will be undisturbed for the short amount of time you need to kill and replant it. You can even drop a note nearby to explain what you are doing so hopefully nobody messes you up.
Also, hang out in Global Chat - people there tend to announce "last egg in (location)", with a link to the location. I do it every time I run across one.