You can use any RNAse-free DNAse buffer. I did try Qiagen DNAse+Turbo DNAse buffer, and try TurboDNAse+Qiagen RDD, no difference.

I am also thinking about making Buffer RDD by myself. But QIAGEN says "Standard DNase buffers are not compatible with on-column DNase digestion. Use of other buffers may affect the binding of RNA to the RNeasy membrane, reducing RNA yield and integrity." Therefore, I guess Buffer RDD is to some extent different from other standard buffers for DNaseI reaction.