Is this book available anywhere for purchase or is there is an online digitial version?
There isn't an online version of it, but it is available in print form, from the Odisha State Museum website. Here is one part of it and here I see another part of it. They're scans of a palm leaf manuscript written in Oriya script.
It's also worth noting that this manuscript may not be the original Angirasa Kalpa of the Atharvana Veda; see here.