Originally Posted by
laura*
Get 1-1/8" parts all around (fork/steerer, headset, stem). The actual sizes may vary, but they'll be meant to work with a 1-1/8" steerer tube OD.
Yes, the OP needs a 1-1/8" steerer to match the 1-1/8" frame and headset but, unusual for the bike industry, all 1-1/8" headsets and steerers have the same dimensions. Unlike 1" headsets and forks where there are ISO and JIS sizes that are close-but-no-cigar.