Thanks.If you just want to fix the existing system easily the old-style bi-metallic strip flaher relays can now be replaced with electronic units like this https://www.autoelectricsupplies.co.uk/product/726 which are not dependent on the current flow to work properly. They will therefore work with any wattage bulbs and even a mix of LED's and conventional bulbs. They are available in 6v and 12v versions.
Says negative earth only but my bike is positive earth.