Hi Josh,
There is no fossicking area at Branxholm, the creek is in State Forest, but a prospecting licence from MRT only costs ~$27 and allows you to prospect in all unreserved public land.
It's the first creek out of Branxholm on the road to Derby. It's easy to miss, if you get to the Mt Paris Dam Road you've gone too far. Look for guard rails. It's a stinky, slimy ditch covered in blackberries, but it has good zircons and the odd topaz and sapphire.