If you find out, let me know!
I seem to be a little less "milkie" this time round, but I still routinely leak through everything. At home I fold a cloth prefold into the top of my nursing tank, when I'm out and about (and covered by the moby) I ususlly fold a cloth wipe into quarters and stick one over each breast.
If I catch it right at the start (the first let down tingle) and apply pressure across my breast (pressing on the nipple and across the breast) I can often avoid leaking. Or at least, reduce the leaking. When I worked at the library I'd sometimes lean forward with my chin on my hands so that I'd look "normal" (or normal-ish) while using my forearms to press against the nipple/breast. And these days I sometimes interlace my fingers and rest them on my chest, again "casually" putting pressure on the nipple/breast. It looks silly, but so does having two big wet spots on your shirt! I hold the pressure till the tingle sensation passes.
But other than that, I don't have any tricks. Maybe get a pair of "my milkies" milk savers so the leaking milk is collected? Not sure how well they work, and they;re not that cheap, but they're basically breast pads with storage built in... "saving" milk that would otherwise leak out and be "lost". Sort of an easy-peasy way of building a milk stash.