FlexWrap
DuPont FlexWrap NF
DuPont™ FlexWrap™ NF is a premium performance, extendable self-adhered flashing material that can be applied over a wide range of building substrates, including non-nailable sheathing materials like PS foam board, fiberboard, concrete masonry unit (CMU) and other such materials. DuPont™ FlexWrap™ NF does NOT require the use of mechanical fasteners in the flexed corner areas when installed according to the flashing installation guidelines issued by DuPont. The "NF" descriptor stands for "No Fasteners" to highlight the fact that no mechanical fasteners are required during installation of this product.
Get the 9" wide version (in a 75 foot roll).
http://www.amazon.com/DuPont-FlexWrap-NF-75-Roll/dp/B004MAFW48/ref=pd_sxp_f_pt $199.54 + $15
TITE-SEAL 9" x 25' Waterproof Flexible Self-Adhesive Flashing
This is a cheaper alternative, but still works ok. It is available in 25 foot rolls which is more convenient.
http://www.lowes.com/pd_375257-81326-TSF925_0__?productId=3539798
$34
(But hard to find in stock)