I couldn't really find a suitable place for this post, so I decided to post here. Are there any products that can make hair thinner or less noticable?

Not really.

Bleaches change the color, but the microscopic bubbling action of the bleach plumps up the hairs giving you blonde hairs that are thicker than before you did anything to them.

So-called Hair Inhibitor creams and lotions and sprays are really just acids and emolients designed to dissolve the hard edges off the hair, and trap moisture in so they are softer to the touch. This does make them less noticeable to the touch, but not the eye, if you have white skin and dark black hair.

Do a search on Jergens, or inhibitor, or bleach and see what others have written.