They don't manufacture a practical commuter for kids so I'm trying to put one together.
Looking at purchasing a used Trek 24" Mountain bike.
However, it has those shock suspension forks.
Where can I find a replacement fork?
Also has flat handlebars.
Would like a more upright, swept back handlebar.
Any idea of a supplier of a kids size handlebar like this? (something like a Soma).
Thanks

Frankly kids outgrow their bikes so often and have so much more energy than we do that I'd say just put on some smooth street tires and call it good to go. If the child is having a rough time reaching that far forward then just get a shorter stem for now and put the longer stem back on as they grow a bit to extend the ownership time of the bike before switching to the next one. The lighter rigid fork and pullback bars may be what us oldsters enjoy but kids are so energetic and flexible that they are likely better off with the stock setups since those setups work better when the bikes are being ridden aggresively. And you have to KNOW that any bike being ridden by a boy or girl that is full of beans is going to be jammed into curbs and ridden down stairs and the like at some point. So the suspension forks and big fat but smooth tires is going to let the bike survive longer between repair sessions. And similarly the stock bars which stretches them out to a proper MTB riding posture will give them the leverage to stay in position far better than a close coupled "sit up and beg" position that pull back bars are going to give.

Also don't forget that for kid's that peer pressure to look the same and fit in is highly important. I seriously doubt that a boy would want to be seen on a mountain bike that has 3 speed style pullback bars and rigid forks set up as a commuter. To be seen on such a bike would produce heaps of ridcule from their classmates and make them the butt of many a joke or even in some extreme cases of bullying. On the other hand I've also seen young girls that will positively NOT even get ON a bike unless it's the right color and has the right stickers on it. So whatever you do I would suggest that you listen to them instead of assuming that what you're doing is going to work out for them on all counts.

24" BMX fork. Check for compatible headset diameter, type (threaded/threadless), long enough steerer tube and an axle to crown race measurement that's in the neighborhood. Might have to check manufacturers sites or call to find such info.