I can probably tell you a number of the CB players who play this tune. You are correct that it is an Angus Chisholm composition. Here is what Kate Dunlay said a couple of years back.

>From the back of the 1978 Shanachie recording, "the early recordings of
Angus Chisholm: Legendary performances of traditional Scottish Fiddling":
 
"SIDE B: (5) TEA GARDENS/MRS. McGEE--...'Tea Gardens' was composed by Angus as he was waiting for a bus in front of a Chinese place by that name in Sydney; he wrote down enough of it on the bus going home so that he could remember and sort it out later. It is the only one of Angus' compositions which he himself recorded."

You're likely to be getting the best results on either Scots-L or CB-Music Mailing lists. There are people there who could probably quote you page numbers of a book with it in it.