There's a no-brainer, cheap option. Find a bike shop that will sell you used parts. Find a pair of Mafac Racers with pivots with no slop. Combine with hangers that are stiff. Use with levers with good throw. I've done a bunch of 27" to 700c and used them. CUrrently I have two bikes sharing a set, both as front brakes. Mafacs are my preferred brakes for slippery roads, esp snow and ice, because there modulation is so good.

My "new" gravel grinder/winter/snow/ice bike now has the combo, Cane Creek levers and Tektro (?) in-line levers. Wow! And completely confidence inspiring anywhere. Oh, and 32c Paselas with 60 psi. You do not want to be behind me when I hit those stoppers.

Ben