You can buy (or better yet borrow to see if you like it) a 1/4 foot for straight stitch machines. I'm assuming your machine is a low shank machine.
I use the seam guide that attaches to the bed of the machine. I admit I'm not much good with a treadle. I'm fine on long straight seams but if I'm piecing little stuff with a bunch of starts and stops I prefer the ease of electric. If you're trying to stay with people power a hand crank machine is nice for fiddly stuff. They aren't much (if any) slower than electric and I think I have better control using one.
Rodney