This question comes up pretty regularly.  Try Decent Exposures and Motherwear
for larger sizes of bras.  I know Motherwear has bras up to 48J.
I would also recommend another lesser known company called Baby Becoming in
Rhode Island.  They specialize in "Maternity wear for the big, the beautiful,
the pregnant and nursing.  Sizes 16-48."  They carry bras in 30AA-60M.  (I
have trouble even imagining that big!  I'm at the little end of that range.)
They also carry slings in long and extra long, too.  Ph 401-658-0688, fax
401-658-3008.  Their e-mail address is [log in to unmask]   The web
site is at: www.babybecoming.com
Cynthia D. Payne
LLL of Berkshire County Massachusetts