Someone on here suggested an on-the-go itchiness/pain healer for those who feel comfort from hot bum soaks but don't always have time. They suggested (& I've tried it many times, it helps me), get a small wad of toilet paper (just a little bit) and soak it in hot hot water. Squeeze the water out so it's not dripping but still hot, and just put it between your bum cheeks right where the fissure is. So you basically rest it right up close to your fissure (if the burning/itching is outside)... For me I'll usually leave it there for a few minutes, even if I'm walking around doing other stuff. It gets rid of the burning for me, just because the hot water is so soothing.
If this doesn't work, soaking in hot water is obvoiusly very helpful. I bought a sitz bath for the toilet seat a year or so ago, was only $8 or so at Walmart. It was an amazing investment

. If I actually ever have time and am in a lot of pain, I use that and it really helps calm pain/itchiness down. For me, I need at least 15 mins on there.
Like someone above mentioned, vaseline sometimes helps calm it down too, because its just soft gooey clean stuff and it's soothing. I use aloe vera a lot but the gel I use (lily of the desert I think) isn't always good when the fissure is burning or itching a lot.
Some would also recommend gold bond powder for the itch and if it's wet down there, but be careful around your fissure area because gold bond = menthol and menthol down there = wow!