I don't think any of his solos were ever transcribed. Stacy Phillips did a couple of things based upon the playing of Bob Dunn (Takin' Off was one of them), which is probably the closest thing you'll find. I believe it was in "The Dobro Book."
I believe Stacy's book,"The Complete Dobro Player", has some note-for-note Dunn transcriptions. Good ear training to do your own! It's amazing what he got out of a simple high bass A major tuning.