Top irons for both standard and 30-31 deluxe roadsters should be available through most of the Model A venders. I usually use Smith and Jones out of South Carolina, and a quick review of their web site indicated that the irons (as well as the bows) are available for each Model A roadster version ($695 - $800 depending on standard or deluxe versions).
As for the 28-29 roadster pickup folding irons, we got a set from Brookville Roadster out of Ohio when my nephew and I built his 28 several years back. I checked their web-site before posting this response, and they are listed as part no. A1075A8S ($1,495 - these are stainless steel versions similar to the 30-31 deluxe roadster irons).
Hope this helps.