Places to find good hobby stuff are everywhere. The key is to keep your eyes open to the hobby potential to everything you see in stores. A bird house if repainted could be a European farmhouse. A little Christmas village could be an American Civil War town. That child’s toy of an underground mole machine could be a burrowing machine as used by the combatants in the First World War. All kinds of interesting stuff is out there in hardware stores, dollar stores, drug stores, and toy stores. Different seasons of the year also feature different stuff that can be hobby useful.
In the winter the Christmas stuff can be very good for the winter wargames. The flocking and cotton used to simulate snow can make temporary snow on the wargame table. The reindeer can be used as both wild and domestic animals. Did you know that in WWII the Germans sometimes used reindeer to two sleds for them? I saw some weird leafless trees that were painted silver and used to decorate some cubicles at work. This would be an easy project to make and then use them for trees on other planets in a sci fi wargame. Trees on Earth are green, but trees on Cestus III might be silver. After Christmas sales are a good time to buy these items at a bargain price.
In the summer there are different kinds of toys. Cheap flying discs can be used for an alien invasion fleet. Toy boats can be used for harbors or coastal traffic, or invasion games. Even if these items come in bright colors or pink or yellow with the new plastic spray paints and some weathering they can often be made useable. In the fall when kids go back to school there are sometimes good deals on school supplies that have wargame applications. Rulers, maker pens, large format paper and even storage boxes to keep little model parts in can be cheaper than usual. In the springtime they often have sales on plastic or other fake flowers and plants. These make the basis for jungles, and other thick forests. A few years ago they had “Easter Bunny” village buildings in HO scale for sale at a local dollar store. Paint over the pastel colors and you would have a nice generic village.