You can get chainrings for pretty much any crank set if you know where to look. I don't have any dura ace myself, but I would guess it uses one of the common BCDs (bolt circle diameter) of the time and there should be lots of options available on eBay or any number of online bike shops. If it's a 144 BCD, as cyclotoine says, you may not be able to go smaller than what you already have. How to measure BCD.

If that's the case, you may just want to (1) upgrade the rear derailleur to something with a long cage, sometimes known as a touring or mountain bike derailleur and (2) change the freewheel to something with a large cog of 34T. Again, there are lots of options on the big auction website and a lot of Shimano choices that would work, if you want to kinda-sorta have things match the Dura Ace components you already have. Here's one example. Functionally, just about any long cage rear derailleur should work fine, and which one you choose might well be determined by how it looks with the rest of your components.

Switching to a compact double up front with say, 48 ad 36 tooth rings would probably cost about the same and has the advantage of letting you keep both your current derailleurs. You should post some closeup pics of what you currently have, then lots of people here would have more specific suggestions.

Your local bike shop guy is a schmuck. No, that's unkind of me, let's just say he' doesn't know/appreciate vintage bikes. Either way, an Eisentraut is far too nice to just toss aside.