I found another love bird that looks just like my lonley male's mate. Are these guys easily tricked into a companion that looks just like their old one or am I begging for trouble with this?

The question isn't so much as to whether he would be fooled, but whether the new female will bond with him.

However silly it may sound, I'm sure the new female's chirps and character would tip him off, that she is not his lost mate.

I would not put the new female in his cage. I feel that it would be better to put her in her own cage nearby, but not close enough to invade each others space. Better to be safe than sorry.

Bad idea I guess. He is doing ok, but is so demanding of attention at times I feel so sorry for him.