Get your "science-y" supplies at Home Science Tools
The kit includes most of the science supplies needed for AMI Elementary Geography and AMI Elementary Biology. If you have Keys of the Universe albums, your materials lists will specify further details. If you have other AMI albums, check those albums for a materials or scan the materials for each album page.
If you have other Montessori albums? I can't guarantee a perfect or even a close match - however, Home Science Tools is a fantastic source for your science supplies regardless of doing Montessori or something different. They cater to small schools and homeschools. Fantastic customer service, fantastic prices, small amounts of chemicals.... Caveat: chemicals can only ship to continental US (check your order contents if you live elsewhere).
NOTE: If you live elsewhere, contact me with your location, and the science supply companies that you do have access to - I'll see if I can set up a kit or package with them for Montessori homeschoolers in your area.