For small batches, like yours, a refractometer only makes sense. The results, using the gravity correction calculator, can be as good as a hydrometer.
FWIW, measuring FG is only important as an indication of gravity stability, the yeast having done their job. If it comes in higher or lower than expected, there is usually not all that much you can do about it.
I bought my refractometer off eBay from one of the larger sellers from the North West. It's the "heavy duty" version "weighing 25% more" than the "economy" model, and surely doesn't feel flimsy. It was around $23 shipped, 4 years ago. It's supposed to have a corrected OG scale, which it doesn't. I haven't seen one that actually does. The scale is large and easy to read. IMO they're all mass produced in China, regardless of what you pay for them, being it $20 online or $65 from a brew shop. Markup makes up all the difference.