This will serve:http://lbtinc.com/three-day-light-jumpable-backpack-11.  The cloth cover for the helmet uses the horizontal strap seen going across the upper PALS surface, and also attaches at the top two loops.  The bottom of the cover anchors in its' zippered stowage compartment.

I bought one of these in Army UCP some time ago, dyed it, and made a small profit selling it here.  I dunno when, if ever, this pack will come on-sale again.  The MSRP is a bit steep, even with Mil discount, but as against that, LBT has a lifetime warranty.  I'd never pay full MSRP for anything LBT sells, even though it is exceptionally well made.  YMMV.