One of those tiny mobile mikes / also clip on your ear that telephonists / football /computer buffs etc use .You can also walk round the room and every one can hear you at the same level.A lady caller used one last Friday at Mick Sheehan's 60th Birthday in Richmond ( Yorks ) she was very good and obviously took all the strain out of needing to shout and bawl in a big room. Acouple of bob investment will keep you in good stead for quite a few years I would have thought .