I'm working on a telecine to digitise my grandfather's old 8mm and Super 8 film reels. To achieve this, I intend to use an old 8mm film viewer/editor (pic related), which I have gutted and equipped with a new bright LED instead of the old 6V bulb. Capturing is done via a raspberry pi with camera, triggered by a switch activated by a small wheel inside the film transport clockwork. Now, I need to focus the image on the (very) tiny sensor of the Raspberry pi camera, and I need it all to fit in the original enclosure. According to my calculations, I will need an f=9,5mm lens for this, instead of the old small lens inside the clockwork, which has too long of a focal distance.

So, TL;DR, where could I buy loose, small lenses? I need a lens with a 8mm diameter to fit the lens house of the film viewer. Would you think this is possible (within the boundaries of budgetary reason) to acquire or would it be better to look for another solution?

Answers very much appreciated. Pic related is the sensor, lens and Super 8 gate assembly