How to get reference from lab I worked with, when lab head seems unlikely to help and I was advised not to ask postdoc I'm looking for PhD but I'm having issues with my referees. I did a placement year and for my second referee I was advised to use one from my placement. I worked only with 1 Post-Doc there but I was told by my uni tutor that I cannot get a reference from him as I need from somebody with a stable/fixed position, here is her reply I asked about that:

"You are normally expected to get the person who officially supervised your research work to write your reference. This must be a person who has a permanent position at the place you worked i.e. the lab leader (so never the post-doc, Ph.D. student or a technician i.e. anyone who is a colleague and not in official charge)"

I was quite surprised, I was planning to simply just use a reference from my Post-Doc. Now that leaves me with my placement lab leader. Well, the thing is she is very strict, moody and hard to please and we pretty much never really talked apart from maybe 1 or 2 short chats. She was away on conferences when I gave a lab presentation and when I had a short seminar. It's a shame, I wanted to show her that I really worked hard in her lab. Anyway, when I left I wanted to personally say thank you and ask if she would be willing to write a reference for me. Again, she was away on a conference so I ended up sending her an email. She never replied. I got too busy with uni and family issues and a month has passed. Now I really want to submit my PhD applications so I sent her another email and now I'm dreading what if she won't reply again? Maybe that was her answer? A 'no'?

Additionally, I got close to another lab leader who said she would be willing to write a reference for me. She also happens to be a very close friend with my Post-Doc supervisor. I wonder if that would acceptable? I didn't work in her lab but she holds a fixed position.

Please help me. On my CV I will mention my placement with my Post-Doc and the lab I worked in, wouldn't that be weird to not provide a reference from my placement lab?

I wonder how much this could affect my application?
One option is to ask the postdoc and professor if the postdoc can write a strong first draft that the professor would be willing to sign (and ideally edit). Most admission committees will probably know that the letter was written by the post-doc, but the fact that it is signed by the professor (in addition to the postdoc) means that the head professor agrees with the assessment. 

This letter will likely be stronger than if only one of the two wrote it because (1) The postdoc will be able to provide detailed examples that the professor doesn't know about (2) The professor's name recognition, through the signature, adds credibility (3) the professor will typically have more experience writing these things and hence he or she may improve the letter by carefully recrafting a few of the post-doc's sentences. Note that (3) and (1) work synergistically. Without the examples provided by the postdoc the professor's experience in letter writing is likely to be less helpful because their letter will sound too generic.

Additionally, this option will also provide the post-doc good feedback for future letter writing (assuming the professor shares her/his edits with the postdoc). So it is really a win-win situation for everyone.