Mountain Biking - Childrens MTB question

So i bought my son (7yo) a used bike this year for X-mas, its in great shape for being 6 years old, but my question is is there "upgrades" available for 20" wheeled bikes, mainly forks, the forks are very stiff i can barely get them to move much, and i like to take him on rides with me and thought it would be nice to get him some forks that actually travel more than a 1/2". Ive tried just doing a google search but didn't come up with hardly anything.
http://i81.photobucket.com/albums/j210/fizzaly/2010-12-22202616.jpg

Yes, you can probably get one from RST, but the cost is prohibative. I'm guessing you obtained the bike at a good price. It doesn't make sense to put a lot of money into a bike so that it lands up costing you more than a new one. I think you might be better off taking the fork to the local LBS and having them rebuild it for you. I can't see that costing more than $50, probably less and they may be able to revive it. The other alternative is ebay.

Yeah the only one i could find was RST also, I will take it to the lbs and see about getting a rebuild kit, i mostly bought one used to see if it was something he would like to do, this weekend i took him on his first "ride" i was pretty amazed how well he did, i took him on a short loop that didn't have much in the way of climbs and he loved it. He wants a fork like mine which obviously doesn't exsist for a 20" wheel so i figured i would poke around and see what i could find.

You could also look into recumbent bike forks.