as you already found, the teutonic alphas (Leica, Swaro & Zeiss) tend to be outside of your price range - otoh older Kowa and Nikon Fieldscope models can often be found with some luck & patience.
With Kowa the models ending in 3 (angled) or 4 (straight) have a fluorite or ED glass element and are preferred, as are the ED models of the Nikon Fieldscopes.
Since you want good low light performance, exit pupil is king (objective diameter divided by magnification) - you want it to be as large as possible for good low light performance.
With Kowa models built during the last 30 years or so, eyepieces are compatible and easily available for all but the 820 series which use different ones and those are rare (Kowa offers an adapter to use small body EPs on them but it's $100). The old Kowa 20-60 zoom with the rubber eyecup is not great and should be replaced - either with the ok current 20-60, with one of the fixed wide angle EPs or in some cases (single digit TSN series from the 80s and 90s) some Opticron zooms fit and are working great.
Nikon field scopes are out of production and EPs are getting rarer, so be prepared to search a bit if you didn't get the EP you want along with your scope. All Nikon EPs are quite sharp, but the zooms are fairly narrow. The fixed wide angle EPs are great.