I use a Campy 8spd Mirage system. Originally a 30/40/50, I changed the rings to 39 and 26, ie the lowest which would fit. It did just about work, but the drop to 26 was too much. The horizontal travel of the front mech dumps the chain onto the BB.
I ened up switching the chainset to a Shimano LX. The Campy mech works well, even with these smaller rings, but with Ergoshifters, any front mech can be used.
I use Marchisio cogs. 28t dissapeared from the Campy lineup a few years ago. They work OK, but not quite as sweet as the real thing. On the + side, you can replace individual cogs when they wear.