In general, Google Maps is probably about the best detailed satellite imagery available to the public for free. But you can also try looking at Bing Maps satellite imagery, which is usually different and could sometimes be newer. From the Bing Maps desktop browser interface, you can right click on a location to copy the exact coordinates, and then paste them into the search bar when browsing for the location on the iNat app or website (or paste them directly into the “Lat” and “Lon” fields when editing the observation’s location on the website).
Or if roads, trails, and landmarks are just as useful to you as satellite imagery, you can browse OpenStreetMap (OSM) and copy the coordinates from there. OSM could be missing some map features that haven’t been visited by one of their editors or traced from Bing satellite maps, but you might be surprised how extensive the coverage is. And if you find something wrong or missing, it’s possible (and encouraged) for you to edit it yourself and fix it.