Some similar bulb replacements are available here:
http://www.thetorchsite.co.uk/Universal_led_upgrades.html.
(UK-based, but take international orders.) I use these, but only with battery lamps.
It is a smaller selection, but the "non-polarity" ones might work directly from a dynamo.
However, I think Reflecalite used to have dynamo-specific versions, but did not say what was different,
so there could be a problem. I think the regulators could be fairly easily made up from Zener diodes and
heat-shrink tubing.
Note: the link above is correct as it appears, but bad if clicked. Copying into another browser tab does work.