I do not have Collins' grammar nor am I very familiar with the notion of
"changeable stems" or what the criteria is for deciding what nouns belong to
this group apart from the examples you listed earlier. Would the paradigms
for nouns beginning with "mano" fit the criteria? If so, there is what seems
to me a full list of 16 such nouns in Pariccheda V. And what about nouns
like 'satthaa" (teacher) and "pitaa" (father) from the stems "satthu" and
"pitu"? I'm not aware of any complete all-in-one list of the nouns you are
seeking but I think the Padamaalaa is a good place to start looking as this
part of the grammar is loaded with declensional paradigms, detailed
explanations, and lists from which you could compile the kind of list you
want.