I've messed with lowline crosses, but then decided to go to smaller frame standard angus.
Here's a place that specializes in smaller bulls. He also has a couple lowlines under black angus and red angus, but if you look for bulls around frame 3, that isn't very big.
For just 3 females, you might consider getting semen and having someone do AI. I found a local dairyman to do it for me, and stores the semen. You just have to know when to call him - if you see her in heat in the morning, have bred at night, and if heat in evening, breed next morning. Or they can give a shot to bring them in heat a certain time.
Many don't want to mess with AI, but works for me.
Save the cost of a bull and feeding him, and fixing the stuff he tears up. You could at least get an unrelated female to your other cows and breed her AI and make your own bull.
Advantage of AI is you can get the best bulls in the world, with more predictability as to what the calves will be. Often the improved performance of the calves can offset the cost of the breeding.
I'm also going red, as blacks don't take the heat as well.
PCC Semen Source