Clevis pins come in various widths and lengths, so you might be lucky. Another option would be to go for bolts, spring washers and nuts, easier to cut to the required length, but these would certainly add some weight.
I remember when I was overhauling my Huret Success set, spring in the FD gave me the most grief, I almost gave up on it. But it's a completely different design than in typical front derailleurs. Thinking about it now, I believe the FD actually used screws, but would have to dig it out to have a closer look and refresh my memory.