I searched everywhere for a big enough baby safe mirror to do tummy time. I ended up making my own.
I don't have a tutorial, but if you can sew, this is just a "frame", like a picture frame, but made out of fabric, in which I inserted the mirror. I made the mirror with a thin sheath of acrylic that my husband bought for me at a hardware store, and mylar.
Mylar is a reflective film used for a lot of stuff, I don't really know for what, but I found it a hydroponics' store. I cut it to fit the acrylic sheet and then used spray adhesive to stick it in place.