Update: If you can't find the .SWF file then try searching just for ".swf" (without quotes). It's a very long URL that starts with "https://bushwhacker2.djartsgames.ca" and ends with "load_method=0" (for me at least).
If you can't get Flash working, then follow the second comment on this forum post. https://www.newgrounds.com/bbs/topic/1489914
You can still play this game. Right-click the webpage and click on "Inspect Element" or "Inspect". Search for ELoader.swf . There will be 2 found, copy the longest url; this is your login credentils. Paste that long url into NewGrounds Player to continue playing. https://www.newgrounds.com/flash/player
 "Bush Whacker Classic"){kind=icon}
 "Pincremental"){kind=icon}