Suntour made a part to attach to that braze on but it only had cable stops, not bosses. Also I think the last one I saw on ebay went for something like $50. Unfortunately you best bet is to get a clamp on housing stop like from Problem Solvers "Back Stop" or use some other clamp on shifter with the shimano stops.
http://problemsolversbike.com/products/backstop
Just put a small stainless screw in the brazeon and use it as stop for the clamp.
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Sugar "Kane" Kowalczyk