Neshkoro is a small town about an hour west of Oshkosh, and a bit south of Wautoma. There isn't a whole lot to it (three bars on the main drag though!), but at least it shows up on maps. That's highway 73 running through it. Please note the road running perpendicular to 73/Main -- that's county road E, and it's critical to getting to Chez Brett.
Do you see that lake at the right side of the map? That's Silver Springs Lake. If you can get there, you're almost to the promised land. If you're coming from the east about twilight, you'll see this sign welcoming you (there's one at the other entrance too).
Follow the path around the lake to Otter Lane, and you're almost there. Then it's just a short trip down Otter to N9189, and you're there. Here's a better look, though I'm pretty sure Deer Haven Lane doesn't actually loop around in the lake...
Can't make it? Here's what it looks like: