This seems kinda silly, but I remember someone here was asking this exact product awhile back.
To be clear, this is for just the pillow and mounting arm, which can be used with various devices. For the steam deck specific mount, you’ll also need this, or their full steam deck bundle.
Alternatively if you have access to a 3D printer, they provide most of their designs here.
Thanks for remembering me! I ended up getting a pillow for iPad.
This looks like a much, much nicer solution. Unfortunately shipping to Portugal alone is 71 euros making this a truly unreasonable price for me. Hopefully they get really popular and come to Europe!