Here is simple bezel insert fitting attachment for hand press. You can turn it in lathe in no time at all. I made this one from aluminium but you can also use teflon or hard plastic. Keep in mind that bezel insert is essentially a spring and it sits inside the bezel because of its inner tension. When the bezel insert is pressed in, it needs to flex a bit - this is why the contact area between bezel and tool is very small and the tool has an 'inside' curve to allow for flexing. (If it was flat, the bezel insert would not bend or flex and it would deform).
The only trick here is to make sure you make the attachment exactly as per dimensions shown here and to finish the top as per photo.
Because my attachment is made of aluminium I place a thin sheet of paper between tool and bezel (not shown on photo) if you make one out of teflon, you can press it directly, it will not leave mark on bezel insert.
Align lume dot with the cut out, place the bezel insert by hand, bring the tool to bezel and then press gently. POP - all done! If you don't have lathe, ask someone to turn this little tool for you. Hand crystal press is available for next to nothing from watch tool suppliers.