slow single strokes with metronomes keeping the space between my strokes even
You are already doing the right exercise...
Another exercise is simply doing the same thing without a metronome. You start at a speed that is comfortable and you gradually build speed while maintaining even strokes. As soon as your strokes become uneven, start over again from your comfortable speed.
Do both of the above exercises with double and triple strokes on each hand, one after the other.
Practicing other rudiments - rolls, paradiddles - will help you in gaining speed along with more even strokes as well, just less directly.
Unfortunately, there is no magic exercise that will help you build speed and maintain even strokes, otherwise - if you could possibly invent another one, you will likely go down in music history for all eternity. Until then, you have to practice and practice and practice - until you hate rudiments and want to punch the guy who invented them in his stupid face...
For free tips and tricks, the best place to look is generally on youtube. This is the first video that popped up for me when I searched "even strokes drums":