Normally for larger sticks like that people buy them from online vendors or pet stores, places that sell them for birds, just make sure to check the safe wood list before buying. For example etsy sells a lot of different ones, as well as pet stores and Amazon both sell bird perches. When people process their own wood they are harvesting branches from their own personal trees or those of someone they know. You need to know what kind of tree it is, so you know it's a safe type as well as know that the tree was never ever sprayed or had any chemicals sprayed around it for the life of the tree (some chemicals can stay inside trees for decades). I guess the easiest way to figure out what kind of trees are which would be to look up online the leaves of safe tree you know grow around you and match them to trees.
Also in case you don't know, once you cut the branches off you want to use (do not use dead sticks laying on the ground or ones with anything growing on them) you need to process them, scrub them clean, ideally boil it to make sure any sap inside is boiled out and anything living inside is cooked out, then bake it in the oven until dry. So do keep size in mind they need to be able to fit in your oven to dry. Freshly cut unprocessed wood is not safe, tree sap is high in sugar which is not good for them, any bugs, bird poop, and/or microorganisms living in or on it could make the chin sick, as well as wood that isn't properly dried can get mold and fungal growth. (ones from stores should have already been processed and be good to go)
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I can't tell just by looking at the pic what kind of wood is in the cage, but I know one popular ones people get that chins love is apple wood. If there are any organic apple orchards near where you live you can ask if they will let you have some of the trimmings when they are doing pruning. Personally I have a lot of poplar and birch on my property so I've use that for most of my perches.
