[sdiy] Looking for a mini rotary encoder with very low torque (servo type)

[Jean-Pierre Desrochers]

I'm looking for a very small (20mm or less body diameter)
rotary encoder with very low torque (servo type).
The low torque shaft is needed because it will turn by means
of a small wheel with rubber sides that will be put against a moving surface, turn and 'follow' 
the moving surface.. no slipping allowed !

The precision of steps/turn is not important.
But the higher will be best..

I was thinking of using a dismantled PC mouse (rubber ball type)
and use one of the two  X/Y optical rotary encoders, but these PC mice
nowadays are hard to find.. So.

I checked Digikey and Mouser but they have encoder too big
for my uses..
The smaller I found has 20mm in diameter..
https://www.digikey.ca/en/products/detail/nidec-components-corporation/RES20D-50-201-1/6469509

Any suggestions ?