i have the yhm flip up rear sight and need a scope mount to clear the buis...anyone have any suggestions

Buy a set of YHM riseers, thats all that I have found.  Also I am looking into a riser bar from rock river, it adds .5 inch to the flat top, but goes on like your a3 handle with two thumb screw.
Hope I helped
Icon

yep thats basically what i need

Try that Wilson Combat Snorkel mount!

I got my riser from MidwayUSA  its a 3/4 in riser that fits on where your carry handle mounts and just like the carry handel has the square pieces under neith to keep it from moving when you change from one to the other.  two thumb screws that are really finger frendly easy to use its matt black and looks and works great . Ive tested it by alighning my 4x12 x42mm scope to shooting 1/2 in groups then took it off shot irons then reattaching the riser with the scope mount and scope back on the gun and it shot the same. the zero return worked great.  its high enough to prob handle a 50mm scope on a flat top with ease but not to high and works great with very low mounts. Price from midway like $20 to your door.  I rate it a 10!

http://www.midwayusa.com/esearch.exe/search?TabID=0&category_selector=all_products&search_keywords=ar+15+riser