I've been searching the internet all day trying to find a replacement master cylinder for my front brake on my 91. I've tried all kinds of searches and looked on all kinds of pages and can't find one. All the ones here on the for sale section seem to be gone already as well. 

Is OEM replacement an absolute must? Pretty much any master cylinder will work. I have a temporary master cylinder from an ATV and white the reservior is a little small, it works just fine.

If OEM isn't 100% a must and you can be flexible for a temporary fix, I'd suggest finding another type on Ebay, or buy a new one from Bikebandit.com

OEM Isn't a must. I've read bore size matters when getting a different one to small and it won't have enough pressure, too large and it will lock up too easily.

No master cylinders on parts bikes on the forum?

I can't seem to find one that's current and will answer PMs sent

I have one.  Someone had spoken up and said they wanted it but that was on 3/20 and I haven't heard from them since.  Send me a PM if you are interested.

-Andy