A while ago, I needed some hold down clamps for the homemade T-slots at the drill press table; eventually, I had three different versions, and they all worked well:
1- First attempt was bending and gluing thin strips of wood
2- Second approach was to cut the shape in plywood
3- The third attempt was cutting the shape in solid wood and adding a pivoting dowel
4- A variant of the previous model consisted of making the pivot with aluminum
Either of the models are easy to make, and are an alternative to commercial hold down clamps; in addition, you could make them in two or three different lengths.