I'd suggest national gymnastic institutes, i used to be able to do the round-off backhandspring full by myself (: i quit gymnastics at nationals. <3
However, since this website doesn't let you post anything other then funadvice websites, i'd say search google, youtube, wikipedia, stuff like that :)
try 3runtube on youtube. They might have one. They do parkour instructional videos, and since it comprises several gymnastics moves they may have one.
Look on youtube; thats where I learned to do that stuff :)