You can conceal a lot of gun with a jacket! I would suggest you look for a pocket gun of some sort for an always gun. If you want to carry a bigger gun without a cover garmet, I would look at some sort of belly band or elastic shoulder holster such as:
http://www.activeprogear.com/holsters.html
Good luck, I have found the Deep Concealment Shoulder Holster works well for me with a reasonable sized pistol. Just have to be sure you don't wear your shirts too tight.
str1