I had something similar happen about 2 years ago, without updating the info here is what I posted on the BF.C forum back in 2007. I hope this helps.
I thought I would wrap up this post and let you know what my search as yielded:
After looking at some of the on-line BMW parts houses I was dismayed to say the least at the prices they were charging for a simple mirror (heated or not) for the E39 (540iT) with standard mirrors. Some of these prices are just unreal for a piece of glass not even mirror glass for my Porsche are this pricy.
Here are the prices that they wanted for the blue mirror glass:
Left Mirror Lens (heated) is part number 51 16 8 119 710
Bavarian Autosport (bavauto.com) wanted $74.95, RealOEM wanted $81.47, Pelican Parts wanted $32.75
Right Mirror (heated) is part number 51 16 8 119 715
Bavarian Autosport (bavauto.com) wanted $71.95, RealOEM wanted $81.47, Pelican Parts wanted $40.75
Guess which one I bought..... close but not quite. I have learnt that the standard mirrors housing and mounting parts are mostly but not all the same for alot of the BMW models of this vintage. If you live in an area where you don't need the heated mirror you could install the blue non-heated one instead.
Even though I live in Canada I bought the blue Left Mirror Lens (non-heated) part number is 51-16-8-119-161-M89 from Pelican Parts for $15.50 it fits perfectly and keep the original appearance. The part arrived yesterday at first I did not think that it would fit because the mirror mounting tabs appeared slightly different than the original but if you look carefully at the corresponding mounting "catches" and carefully align the parts they will click into place and hold securely, the fit is perfect just like the original. The blue Right Mirror Lens (non-heated) is part number 51-16-8-119-714-M89 for $21.00. By the way, if you purchase the non-heated mirrors like I did you can just tape up the loose connector and secure them out of the way within the Mirror housing.
PS. I hope this write up will help someone save a few $, why get ripped off if you don't have to for a piece of glass, just because it's a German car. If you are ordering the parts from Pelican Parts for another BMW model make sure you check/use the parts cross reference description just before you check out, this tells you what models the part will also fit, this is how I was able to get most of this info. As well, if you order on line from Pelican Parts they offer USPS shipping to Canada (lower brokerage fee $5)
Before I got the 540 I never had heated mirrors so I haven't missed them. Any how, I don't know if your car has heated mirrors or not...so you would have to check that out.
Edit: Oh ya since then, the prices have changed the updated price on the Pelical site for the Blue Right Mirror Lens (non-heated) part number 51-16-8-119-714-M89 is $23.25 and for the Blue Left Mirror Lens (non-heated) part number is 51-16-8-119-161-M89 from Pelican Parts for $17.25
Left Mirror Lens (heated) is part number 51 16 8 119 710, Pelican Parts price $32.75
Right Mirror (heated) is part number 51 16 8 119 715, Pelican Parts price $36.00