The Continental shifting itself could simply mean that you need to tighten the nut holding the shifter.

Bar end shifters are pretty easy to use, and you would have the choice of getting newer Shimano (assuming your drive train is Shimano or compatible SRAM) and having it indexed or going old school with Suntour Power Ratcheting. The Suntour would be about $25-35 used and the Shimano would be a bit more.