wald white block pedals, ebay:
VINTAGE WALD 6140 WHITE BICYCLE PEDALS - eBay (item 280400793815 end time Sep-29-09 17:14:55 PDT)
or, these white block repros from chain gang lowriders:
Pedals
if you're looking for a "period correct" look, you gotta take off the reflectors. i think those didn't become mandatory till the early 70's.
all the harley bikes i've seen from the early 1900's all have black, block pedals. probably torringtons. just search ebay for "torrington pedals" and a bunch will come up.
if you want the look that "seattle rider" above is talking about, search MKS sylvan pedals. they might not come in 1/2 inch to fit one piece cranks, though.
good luck.