There's a similar thread going on the Calvert Stevens CS88 that shows a varient of the screw you want (the CS88 version would fit your plane).
You best bet would be to try people who supply second-hand parts, or to have one made. Neither option is likely to be cheap :roll:
I have a Record-Marples SP4 (handyman version of the Record 04) - dating to ~1995-98 which has the same groove machined in the bottom of the frog, but the base has not been tapped for the screw. Apparently the SP4 didn't come with an adjuster (so why machine the groove in the frog? #-o ).
The two piece cap-iron is worth having, IMHO (people either love them, or hate them with a passion). You could even keep an eye out for an older Record or Stanley and swap the cap-iron into the better, older plane. Your plane is too new and therefore the chances of a sh#tter are much higher - 'though you may have stumbled on a good one.
Cheers, Vann.