I don't know where between here and there is as your location but I happen to live at the confluence of two major rivers, the Snake and Clearwater Rivers at the SE corner of WA on the border with Idaho. these rivers drain off of millions of acres of national Forest and have numerous large tributaries. I just go down to the rivers and search for old water logged pieces that suit my intended design. I do scrub the wood with a wire brush, pressure wash, then scrub with bleach and let it sit for a couple hours. Then I rinse in hot running water and put it in my tanks. The beavers already have eaten all the bark and trimmed the branches in a way that renders a very natural look. I know I am lucky to live by such clean rivers full of wood. The hard part is finding very old, hard, dense, water logged pieces that may be many decades old so they are already aquarium safe.
I sieved my own substrate from a high mountain stream which has water with a pH of 5.1 and is incredibly soft, an unbelievable 15 ppm TDS. Perfect wild Discus water only 135 miles away. I never expected that but I decided to test it on a fly fishing trip. Sand from a stream like that should be safe.
I considered buying some wood but the cost of the freight is as high as the cost of the wood.
Maybe somewhere between "here and there' you have some clean streams which contain usable wood?
I just set up a 125 gal and I know the wood I found would have cost me about $200 to buy and have shipped based on what I saw for sale on aquabid.com..
I'm not sure there are any clean rivers or streams left in the northeast. However, our water supply is almost as soft as your water BUT nowdays it is protected by people carrying guns - Nobody allowed near it.