You asked about

• Ptorch--I've seen it every time I've started the Caves from scratch
• electric lamp--found it every time on the AT Road side of the teleport
• electric eye--never seen it; suspect it doesn't exist
• loudspeaker--ditto, never seen
• High voltage transformer--to distinguish from the similarly named device, I call this HV Transformer; never seen
• demon doll--in R. Castle, in the cellar (IIRC, you need some sort of key to get it)

Electrods: Anna and Crock always have 'em if you've patched the game to the most recent (sometimes, if you enter Arnika at extremely low level, you won't see 'em yet). If you haven't patched the game yet, be patient; eventually Anna will.