Patching and Plastering - looking for a spackle/plaster for a mural project

I need to find a spackle or plaster for a restoration project I am working on. The mural was painted in 1929, and there are missing plaster areas, which need to be filled. I have been told to look for a product that has these characteristics:
1) glass balloon filler (very low shrinkage if possible)
2)PVA emulsion
3)close to a neutral ph level
4)water based binder

The depth of the area measures about 1/4" and some areas are 12" W X 36" H.
I will be inpainting the missing areas after sanding the fills and isolating them with B 72 acryloid. Thanks for any help you can give me.

I don't know if it meets your specs or not but I usually use durabond for plaster repairs. It's a setting compound so you have to mix it with water and it only has a specfied pot life. It dries hard and doesn't shrink much but it is hard to sand. It pays to apply it neatly!

thanks so much for giving me a name of a product,. I will look it up on line to find out more about its compounds. I appreciate the response. Thanks again!