Not a Wald, but as as big despite different dimensions as the Wald Newsboy: I rigged up a quick-on and quick-off system for a large basket and the rear rack on my Dahon Hon Solo. The basket is a 15" X 18" (at top; the basket tapers toward the bottom) steel wire storage container from Target or Office Max, forget which, part of a modular storage system for home or office, inquire within, recommended by experts. After considering or trying alternatives, I settled on this:
A 2X4 block cut and rasped and filed to fit snugly in one of the central gaps in the rack's top; block bolted into place on the wire bottom with steel plates.
The forward lip of the basket butts against the Carradice SQR block on the seatpost, which keeps the rear of the basket from lifting -- so to lift pushes said forward lip against said SQR block, and it can't go anywhere. The SQR block is there because I also use a Camper Longflap and Junior in QR mode, depending on bulk of load.
A toe strap (am looking for more elegant, "click-in/out" type of alternative) keeps the basket down in front.
This basket has sufficient area on the bottom to hold 4 standard paper grocery sacks, full.
A cargo net zip tied to rear and hooked in front keeps groceries from flying off in the whirlwind of my passing.
Altogether, a very cost effective and elegant solution: Ignoring the rack, the commodity basket cost well under $20 ($15?) and the hardware to hold the wood block in place cost just a few dollars at True Value. The toe strap was sunk cost.
I've carried gal milk, 12-pack beer, and 2 pretty-fullish paper sacks, all at one time.
I personally am not of the basket-first-choice cohort (I like Ortliebs and f or rear racks), but for this beater grocery/dog run/carry on trip bike, this QR basket system answers a question I've had for at least a decade.
FWIW.