I like that Campy triple -- keeps with the Campy blood on the rest of the bike, and the 30/24 would be lower than the 40/30 on your Motobecane. If you have trouble finding a chain that works with both the 5-speed block and the "10-speed" crankset (chainrings are generally spaced closer together now), you could pick up chainring spacers to scooch them apart from each other a little when you bolt them on.

I thought I heard that the TA tripleizer was out of production, but maybe it's one of those things that goes in and out of production with demand.

Editorially, I think it's unfortunate that popular biking culture looked down on triples (and the people who use them) for so long. Yeah, they weigh a little more and have a wider Q-factor, but it's much healthier to have low gears available when you need them.