We have a appasamy Zeiss type 3 step slit lamp. The LED bulb fused one fine day and appasamy was not able to immediately supply the same. So searched and ordered on Amazon. Replaced by local electrician with soldering for 50 Rs. Now i have about 8 in spare. Total cost was < 250 rs.
First open the black plastic screw at the bottom here
Then you have to remove these 5 screws. I dont have the photo of the inside at present. But its fairly simple for a local electrician.
These LEDs can be ordered off amazon. Very cheap. One major issue is these are bluish white and not yellowish white. So does alter the colours a bit. But this is a good option in the pinch till the time Appa guys get the bulb to you. :)