Even some cheap ones allow brake mounting. A $15 no-name thing I got at the LBS has three sets of holes in the front. The middle set is for brake mounting.

I'll echo Mauriceloridans' comment about stability. With even modest loads in the panniers, the rack becomes subject to sway. It's fine for lightweight stuff, and occasional heavier loads. You're better off with P-clips on the chainstays (not the seatpost).