I've been using the Martin Fields Overlay Plus (
www.overlayplus.com) on my Axim X30 and it's really nice. Of course, I like the clear overlays, not the "anti-glare" ones that make the display fuzzy and less colorful. If I get glare, I move my PDA 2 degrees. Small price to pay for a view that looks like the original screen.
Anyway, I've emailed them to see how long before they have an X50 overlay; they don't yet have the X50 in Asia, but they figure as soon as they get their hands on one (ETA late November) they'll have one out in a few days.