Open IrfanView, should have black screen.
Drag picture onto screen
Click on ‘File’ in top left bar
In the dropdown menu, click ‘Save as…’
Two boxes appear
In box ‘left’ I change File name, so as not to replace the original.
Indicate where to save file in ‘Recent folders’ dropdown menu
In box ‘right’ tick ‘Set file size’ Put in 499
Press save in left box
Mine turned out as 490KB file size
Hope this works for you
Alan (Using Windows 11)