Otto Musica's Muco shoulder rests are very comfortable, thick, soft, yet sturdy, medium-firm foam. 

Ergonomically and economically priced.  Available in multiple models to fit 1/8 sized violins through 4/4.  Removeable feet. 

SR-1 - Fits 1/8 through 1/4

SR-2 - Fits 1/2 

SR-3 - Fits 3/4

SR-4 - Fits 4/4