Both sun visors don't stay up. Any ideas to fix that?

you could make a clip-like device to help it stay up better?

I would suggest take a one inch wood screw and screw it into the side of the panel next to the visor. Raise the visor and slide it to the left over the screw. The visor will now be resting on the screw. When you need to bring down the visor, slide it to the right away from the screw and lower it....It is a little inconvenience, but it works for me. Put one on the passenger side if needed. The only problem with the passenger side is most passengers will just grab and pull down, so you will have to advise the passenger or lower the visor for them.