There are numerous bushes in the shifter mechanism and 2 or 3 at the gearbox end. Notchy gears could be worn synchros or it could be worn bushes. After replacing the gearbox oil I found gearshifts to be noticeably smoother but best to rule out bushes first as that can be done by just looking at them and seeing if they have excess movement.
VW doesn't sell the bushes only the whole cable or shifter mechanism which are quite pricy. If you need bushes dieselgeek seems to be the place to get them, however, they only ship from the US I believe.
This video goes through basically all of them:
https://www.youtube.com/watch?v=7HBE5vycg-4
Hope that helps
