sustainer \sustain"er\, n.
   one who, or that which, sustains. --waterland.
   1913 webster

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

104 moby thesaurus words for "sustainer":
   maecenas, abettor, admirer, advocate, aficionado, alpenstock,
   angel, apologist, arm, athletic supporter, back, backbone, backer,
   backing, bandeau, bearer, bra, brace, bracer, bracket, brassiere,
   broadcast, buff, buttress, cane, canned show, carrier, cervix,
   champion, commercial, commercial program, corset, crook, crutch,
   defender, dependence, electrical transcription, encourager,
   endorser, exponent, fan, favorer, foundation garment,
   friend at court, fulcrum, girdle, guy, guywire, jock, jockstrap,
   lover, mainstay, maintainer, mast, neck, network show, newscast,
   paranymph, partisan, patron, promoter, prop, protagonist,
   radio fare, radiobroadcast, rebroadcast, reinforce, reinforcement,
   reinforcer, reliance, rerun, rest, resting place, rigging, second,
   seconder, sectary, serial, shoulder, shroud, sider, soap opera,
   sound effects, spine, sponsor, sportscast, sprit, staff, stalwart,
   standby, standing rigging, stave, stay, stick, stiffener,
   strengthener, support, supporter, sympathizer, taped program,
   upholder, votary, walking stick, well-wisher