I can't tell you specifically how to get your grant. If I were you I'd check with the more experienced teachers, your administrators, or browse the net. I'm sure someone there will know how to get money.
Until you get it, maybe I can give you some survival info.
I did what you are doing for eight years in Arkansas. I don't think there is a whole lot of difference in the two states. My subject was Social Studies and I had special ed. grades 6 - 12. I had no money either. I also had no texts because of course the kids couldn't read the regular texts or they wouldn't have been in my room.
Kids don't qualify for special ed. Science or Social Studies. They are there because they qualify due to reading issues. So I was really teaching reading, just using Social Studies materials to do so.
I started by begging and borrowing from the elementary schools in my district for cast off books of lower reading levels. I survived a month or so with those, then I convinced my supervisor to buy some low-reading-level, high-interest books about the wars. Then I taught History around the wars. All the time I was absorbing info from the more experienced teachers. I looked for projects that gave me lots of learning bang for my buck. Example.. family history - draw family tree and interview older relatives (Science - go for genetics) Salt maps to learn Geography (Science - focus on mountain vs. flat)
I'm guessing you want to do hands on activities and you need supplies. If their is no rule against it, ask parents and churches. They may be "separate" but I always found the churches to be quick to donate to the special needs kids.
Sometimes, elementary teachers have elaborate kits that come with their Science texts. If you're allowed to use district wide email, then ask for discards, extras, and left overs from the other classrooms. You might be surprised what turns up.
Judging by the date on your post, you're well into your first week and I hope it is going well for you.