Check out the Kool Stop BMX or Mountain brake pads for rim brakes. I had a pair of mountain pads on my bmx and they worked excellent. They're also extra long for more power!
My BMX has fly u-brakes, clear pads, odyssey gyro and levers on chrome hazard light rims and the stopping power is better than any other BMX brake I have ever used even compared to a straight cable set ups.
Salmon pads are amazing and often overlooked as clear pads have overtaken the BMX pad market. I've been running Salmon pads on black Birdcage rims for half a year and they even stop half-decent in snow/general crappy Canadian conditions. The Salmon compound used by Kool-Stop (but invented by someone else) actually revolutionized the rim brake pad market like 30 or so years ago, so maybe worth checking out if you've never experienced smooth, powerful brakes on a BMX.
Clear pads are more on/off powerful when they're dry, but in wet conditions, Salmon pads are more consistent and predictable.