OK. I don't have a pair of SH-M034's in front of me, so I may be talking out of my butt, here. Still...
There is nothing all that special about most of the screws and bolts used on bicycles. You can probably get a replacement at any hardware store. Take the other bolt with you so that the helpful hardware guy can find one like it.
Not too long ago I needed a bolt with a 3 mm allen head to mount a rack. The hardware guy looked skeptical, but he found one. It cost me 15 cents.
Get a stainless steel bolt if you can, and put a little blue loc-tite on the threads before you screw it into your shoe.
Good luck.
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Religion is a good thing for good people and a bad thing for bad people. --H. Richard Niebuhr