Rivendell used to sell the Simplex retrofriction shifters, but the supply dried up. They're the best friction shifters ever made. There are a couple of sets on eBay now. The auctions close tomorrow. I prefer the older "sunburst" style. I need another set, so I've been watching them. The last three sets went for $22, $36 and $61. The $61 set was NOS.

I'm planning to try setting them up as barends, using the Rivendell pods.