Worn Speedo

Being new to all this, I purchased a new speedo from ebay that stated it fitted my '85 109 FFR, on fitting it I found that that the drive was incorrect,:doh: so assume (I know it makes an ASS of U and ME!!) it was the wrong one!
So i decided to take the old one apart and found the worn part! The initial cog that counts the miles! Small white cog with course teeth. The actual speedo works, it just doesnt count the miles.
Does anyone know where I can get one or even have one??? It's shown here in the new speedo in red with fine teeth.

Cheers for help

Mart

On the back of the speedo is the part number, try searching using that on eBlag or spares sites, maybe a scrappy.

Many thanks, might have it sorted!

Cheers