Need Parts for an older Baby Lock Serger

Question

I have an old Baby Lock Serger that needs a part for the air threading lower looper (inside the machine). I have searched online and can't find a description anwhere of it. Can you tell me where I may find this part to fix my machine? I bought it used, and it is missing one of these tubes or hoses, whatever it's called. My sister has a machine just like it and we know what it needs, but don't know where to get it.