I would be a little reluctant to drive it at 4.5A, sometimes the tail switches are rated to only 3A. Looking at Match’s data on the emitter lumens (XM-L ) the difference between 2.8A and 4.5A is about 150 on a 1C. Ideally you would drive it at about 3.8-4A since that is where the curve peaks, additional current doesn’t translate to lumens.
There’s one at intl-outdoor that looks pretty good, $17 and you can choose smooth/op, T6/U3, and modes, but then again I think you can build it for about $10 with parts from fasttech