In this price range there are already a few worthwhile pieces, although ultimately, if you really need a spotter you should be ready to spend a fair amount of cash and I would recommend you extend your search to the next price category.
I will segregate these spotters based on the objective lens diameter.
Leupold Gold Ring 10-20×40. This is one of the smaller spotters on the market that doubles as a pretty decent monocular.
Minox 16-30×50. This spotter impressed me with how sturdy it felt and how decent it was for the price. It is compact, but beefy with nice glass.
Honorable mention : Leupold Gold Ring 15-30×50. This is a testament of what you can do if you do not push for especially ambitious design. This spotter is a little longer than the current crop of 50mm spotters, but that allows it to deliver very nice image without resorting to exotic glass types or super complicated lenses.
Nikon 16-48×60 XL. Another strudy offerrign with decent performance. This is a fairly decent field spotter with a somewhat unconventional form factor.
Hearsay recommendation: I heard that Alpen 20-60×80 spotter is kinda OK, but I have not seen it myself.