The knitting garden says that Wool Cotton is DK weight, which is, I think two sport weights, less than worsted, though. So, you might have to do some serious math if you are substituting a worsted, unless you can get it to guage right, you will have to make a guage swatch and use different needles, though. Lion says Microspun is DK, but I strongly advise you not to get it. I tried to use it on a bikini top, I only got one triangle done because the splitting frustrated me so much, it had broken and tangled pieces in the middle of the ball ugh. Babysoft might work, I haven't tried it, and it depends on how much you like pastels. Why does it seem like if you find stuff that thin, its always in pastels?
Good luck with whatever you find works for you.
I've used Simply Soft and think it's closer to DK than worsted, so that would be good to substitute. And it's reeeeeeallllyy nice and soft!