+1 on the ebay search for parts, though it sounds like your shop would be less than enthused to service it for you. Also, having serviced a few of those lower end brake/shift levers, I can't really recommend a diy approach without some hands-on guidance.

All that being said, this is a poor reason to replace a bike if that was what the shop was indeed suggesting(?) I would question both the integrity and intention of a mechanic that advised this. Finding replacement brake/shift levers should be easy to find for well under $100 of that era.