found a few sites recently, by accident, which may be of use to some (especially those down-underish):
Driwear Incontinance Products | Plastic Pants | Rubber Pants | Incontinence | Adult Diapers
that's a N.American site, but they ship abroad.

Home page
Australia and New Zealand

Victoria Healthcare Melbourne | Disposable Incontinence Products
'Australia-wide'

i've not tried any of them, but, if you have, please comment, for the benefit of others (personally, i'm interested in the Driwear products, if shipping and customs aren't a problem).