If you don't want to learn to crochet just for this (but I'll still try to corrupt you later
) try one of these for the dcs:
Knit the stitch, then slip it back to the left needle, purl it and slip it back, knit it and go on to the next stitch. If you knit it all three times, it'll be taller, but if you're using garter stitch for the border it won't look as good.
Yo, knit the stitch where the dc goes, slip back, k the st and the yo tog, and if you're binding off, k that tog with the stitch on the needle.