Ok how about defining it as malts that are either not bottled by the owners or where maybe only one expression exists but is not actively marketed. A provisional list of Scottish distilleries:
Allt-á-Bhainne
Auchroisk
Aultmore
Balmenach
Benrinnes
Blair Athol
Brackla
Craigellachie
Dailuaine
Dufftown
Glenallachie
Glenburgie
Glendullan
Glen Keith
Glenlossie
Glen Scotia
Glen Spey
Glentauchers
Inchgower
Linkwood
Macduff
Mannochmore
Miltonduff
Mortlach
Strathmill
Teaninich
Tormore
I realise that this is a long list, but a lot of these are hard to find so a bigger list means that more folk might have some of them. Also I'm perfectly willing to concede that some of these have established a substantial following and could be knocked off a list of obscurity (e.g. Mortlach, Linkwood, Glen Scotia, Benrinnes). Any thoughts?