Judging from the wheelbase and graphics the bike looks like an early to mid '80s model. I suspect your looking for an old DiaCompe brake.

But as Airburt says you could likely use a brake like some of Suntours last models that didn't use the holes.

I believe the adaptor plates Xenologer is talking about are for use if the stud unscrews from the braze on portion. I don't see wrench flats on yours so I am not sure if they would.

I think this is something like you need or close to what came on the bike. but the ebay seller wants $200 http://www.ebay.com/itm/Dia-Compe-96...item19d145ae74