I've used a few different types of covers but didn't like them cos they added bulk to my bag under my clothes. A much simpler idea (if you're planning on using a cover to stop your skin from sweating from the plastic of the bag) is to purchase some baby bibs. Tied them around the bag and put them between your bag and your skin, this will absorb any sweat.
You can always make them yourself (or have a friend who sews make some for you). Just use a bag as a template. You can use up any scraps of material you may have lieing around and it's much much cheaper than buying them ready made.
Failing that, there's a few companies listed at http://www.ostomates.org/links/access.html
where you can order them over the web.
I have had an ileostomy for 31 years now due to UC.
Moderator of the Ostomy Forum
I'm not a complete idiot - some parts of me are missing!