Best type of arm cushion?

Hi! I’m currently using a flat rectangular pillow during blood collection at my workplace, and sometimes the arm of my patient (even the AC area) will float instead of being able to rest on something. This also causes some bending of the elbow in some patients who don’t care to keep their arm straightened (even when i ask them to and try and adjust their arm too lol).

Would a triangular arm wedge be better? However if my table and the patient chair are not adjustable in height, would a triangular wedge be less ideal? I’m annoyed with the rectangular pillow hahaha at this point i kind of want to get a better pillow at my own expense 🙃

What do you use in your workplace, and how do you avoid floating arms? Thanks in advance!