i have ordered this new 20 Watt LED illuminator for the Zeiss IM/IM35 microscope from a company called www.retrodiode.com in the USA. They have just emailed me to say that it is ready to be posted to me. The following are pictures of my actual device, 3D printed to fit this microscope. The equivalent halogen illumination us apparently > 100 W halogen bulb and should therefore provide good illuminator for dark field work (currently I am limited by insufficiency light at higher powers in dark field using the 60 W tungsten illuminator that comes with the microscope). It should also work for fluorescence if I ever go that way. Zeiss themselves recommended using two illuminators with mirror device between them to combine the light but this combination device is very expensive on eBay – seem to be very few around. Therefore the modern LED retrofit is the sensible and much cheaper option.