is the stock plastic or wood? if the woodgrain is molded into plastic or rough enough in the wood that you can feel it dragging your fingernail across it, then you can simply rub some black shoe polish paste into the woodgrain. buffing it with a rag rolled into a hard ball will remove the polish from the high spots and leave the grain dark. even the bright metal sides can be done this way. its not permanent in any way but it holds up fairly well, and can be touched up at any time.
a scope like the old fashion long tube type could be made up from a long piece of copper pipe and a reducing coupler for the eye piece. get two brass saddle type pipe hangers and bolt them to the top of the barrel so the scope can be held in them, you don't even need to joint the coupler to the pipe if the saddles hold onto the two pieces.