The holes are pretty standard, they just all have a maximum size. (22ga, on all I have seen specs for.)
How about using a vise to flatten the ends of the pins, then trimming them to fit? (Make sure the flatness is parallel to the contact openings, that is, perpendicular to the long side of the breadboard.) If they almost fit, you might even get away with using diagonal cutters at a very shallow angle to trim the leads to a point.
With that said, I can't imagine that a breadboard-friendly circuit could be so sensitive to soldered-on pins. A breadboard hardly has tightly-controlled characteristics as it is.