The Collaborative International Dictionary of English v.0.48:

Upholder \Up*hold"er\, n. [Up + holder. Cf. Upholsterer.]
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   1. A broker or auctioneer; a tradesman. [Obs.]
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   2. An undertaker, or provider for funerals. [Obs.]
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            The upholder, rueful harbinger of death. --Gay.
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   3. An upholsterer. [Obs.]
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   4. One who, or that which, upholds; a supporter; a defender;
      a sustainer.
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WordNet (r) 3.0 (2006):

upholder
    n 1: someone who upholds or maintains; "firm upholders of
         tradition"; "they are sustainers of the idea of democracy"
         [syn: upholder, maintainer, sustainer]