I wear a tux pretty often on gigs and my carry gun is a P3AT concealed under my cummerbund. No reason a J-frame wouldn’t work, too. I carry the gun in an IWB holster clipped inside my pants at 1:00. I also carry a stun gun in my left front pocket.
If you don’t have to worry about taking your jacket off (we frequently take off our jackets because the stage lights get so hot), you’d be able to wear just about anything if it wasn’t for the fact that tuxes don’t have belts.
A good tux is usually light weight and suspenders show through the jacket. A shoulder holster might be kinda obvious to anyone looking for guns.