One way of locating 900-strength players is to use View Players, (starting at around page 1400) and noting which players were Last Online within the last day or so. You could then review their profiles. (Actually, you can specify the rating range you are interested in).
Equally, you might consider games against a stronger opponent - employing either TAKEBACK or another ability-balancing scheme.
Hey all. Not going to let my 8 year old girl play unsupervised games on here obviously, but I think it would be great to find another young kid just starting out that she could play some supervised games with. I'll probably create an account for her for this purpose.
Estimate of 900 strength is based on her rating at chesstempo.com where she started doing problems a few days ago. She seems into it and will likely improve rapidly but right now, well 900 is 900 :)
Let me know!