The weather has not been great down this way the last few days and it is pouring at the moment. The easiest access is right next to Hampden bridge. There is a sandy and gravel bar right next to where you walk down, but this is generally better after a flood. You can walk up or down stream a little and still find bits. I have had more luck down stream, but crossing the river may be difficult with the rain we have had. Mostly petrified wood and jasper to be found, but there is also the occasional small piece of agate.
There are other spots well worth a look, but would depend on how much time you have.
Any creek crossing from Berry to Kangaroo Valley is worth a look but can be very hit and miss, also be careful of private property.