Is that Bellata near Narrabri? Sorry I can't help with specifics, only ever passed through, never fossicked there. I can see quite a few references to the existence of all the things you mention around Bellata but don't know specifics. Looks like a volcanic region anyhow and has the same lava types as the spots I find the things you're after up here in CQ..
Hopefully one of our other member has been there and can chime in
Most of the Dirt roads in the area have Agate.... All you do is find a dirt road and start walking down the sides. No Agate, find another dirt road.. Further you go out, less chance somebody has picked it over. Any freshly Graded road is a good spot to start. Most are smallish in size 1-3" but you do find larger ones sometimes.... But Do Not Dig in the road, they don't like that... Im lucky as my Mate has access to a Quarry that most of the ''roads'' comes from. Sorry, but its on private property... you can also find them in the paddocks... With Farmers permission of course.... Good luck in the hunt.... Some of them are very nice specimens....
And don't get lost...easily done out there
LoneWolf....