While I use it mostly for intimate mornings, I think you'd find the Ostomy Secrets belly band would work great. Wearing your bag in the normal vertical position, it will then tuck into a pocket in the band holding everything tight to your body.

Posted by: @rick

 Seems all stealthbelts as for side ways wearing.

I've been wearing the VERTICAL Stealthbelt now for nearly a year (a review is pending), and I really like. It does keep a lower profile at the expense of some added bulk (i.e. it uses a wide band to hold it in place).

A belly band, or similar product, as goatherder suggested, is also an option. 

But you also have to be realistic with your expectations. A full bag will be noticeable no matter what you wear under your clothing, but many of these support garments/bands can really flatten the appearance of an empty or somewhat empty bag. 

Some illustrated examples can be found in THIS article, and then several of my Guide to Ostomy Accessories further expand on those options. 

An athletic 3way stretch tee shirt fixes this with minimal bulk.

Eric,  Good article !

Do you ever find the band rides up or down on your abdomen ?  

Posted by: @dlkfiretruck

Do you ever find the band rides up or down on your abdomen ?

Ostomy wraps do, but none of the StealthBelt products have moved up, down, or sideways 👌

@veganostomy which do you find more stream line the vertical or the horizontal stealth belt?

@cygo With my shirt tucked in, the horizontal is my preference. But for casual or cycling, I do enjoy the vertical belt a lot.

Both will bulge as the bag fills, so I tend to keep them as empty as possible since there's no hiding a full bag regardless of the orientation.

The vertical, however, still has a tendency to "show" below my shirt, since it does hang down lower than my shirts do. Since it's black, it blends in without being too obvious, but it's definitely not as stealthly as the horizontal stealthbelt :)

@veganostomy Good to know! Thank you Eric!

@dlkfiretruck I use a wrap from ostomy secrets every day, all day long (except to sleep) and it keeps things hidden very well.  It can ride up or down while sitting for a while, but I've just gotten used to adjusting regularly.  I don't even think about it anymore.  I don't think I have ever been out in public without my wrap.