I saw a YouTube video showing a tool to straighten bowed hardwood flooring. You screwed one end of the tool to anchor it to the subfloor and then turned the middle to drive the head of the tool into the bowed board.

My question is:where can I buy one of these tools?

Thanks,
Scott

If we can not straighten out a board we usually cut it in half and then either start a row or finish a row with the two pieces. A long board will be easier to straighten because you have leverage on your side. A large screwdriver big enough to take the strain of prying will move a board toward it's place. Then you can fasten the spot with your choice of fasteners, a staple will be best. Move along the board until you fasten it tightly. You may need to file the end of the screwdriver so it can sink into the sub-floor with a tap of the hammer, angling toward your last row.
Been laying floor for a long time and haven't needed a board straightener, maybe I just haven't had to lay anything wider than 8 inch solid, wider plank may not straighten out so easily.
I bought a wide plank straightener at a yard sale and it's a fine looking tool,
but I haven't needed it.

I found the website for the tool. Www.Originaldevices.com

. . .if you flooring is Wide / extremely bowed ?
Turn the board over and kerf the back-side (7/16" depth) kerf spacing will depend on the severity of the bow & the species.

Here is a tool I made to straighten boards.
https://youtu.be/Ycy8U6ZhqMA