float bowl screws, or float bowl drain screws?
For a list of every screw size you need to replace every external screw (and some internals) with allen socket ones check out the macgregor carb cleaning manual.
If you need float drain screws - you can get them here:
http://www.siriusconinc.com/pro-detail.php?pid=&product_id=3325 as well as other sources. Sirius is local to me, so shipping is actually free to me which is why I use them so much. If you're in the states you can likely find things cheaper if you research. Every source in the states seems to gouge me on shipping (I'm in Canada).
1981 CB750K with 900 cams
90K KM's, rebuilt head, rebuilt carbs, upgraded valve stem seals
My wife's recipe website that I'm trying to help promote:
Strawberries for supper. Yes, I am a lucky man.