As a middle school teacher I am constantly looking for money for my students and STEM program. Here are some that help:
Lowes toolbox for education: this will help fund the bed and fill for the bed as well as gardening and assembly tools that may be needed for multiple students. WHen I did this I actually ended up with several thousand dollars worth of equiptment and a small greenhouse.
http://toolboxforeducation.com/
Homedepot
https://corporate.homedepot.com/grants/community-impact-grants