My mistake above.....thought he still had the original hub. Doubt he'll find any 6spd HG cassettes. Might be time to retire the 6spd index shifters and go to more cogs. I assume he still has a 126 rear. Sheldon's selling NOS 7spd 105 hubs (mentioned above somewhere) that will take UG (6spd) or HG 7spd.....or an easily altered 9spd cassette (leave off cog and spacer).
Should have questioned OP for more info before making suggestions. Oh well.
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..... "I renewed my youth, to outward appearance, by mounting a bicycle for the first time." Mark Twain, Speeches
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