Sorry, my bad for not being thorough enough to verify availability of appropriate sizes. It looks as though you could also do this within budget at The Compass Point in the UK with a pair of Silva Montana o-pants and a colour-coordinated Silva Eclipse top, the former being available in size 1 and 2 (intended for 8 and 10 year olds, respectively) but the latter only in size 1. Or they appear to have stock of a Trimtex top the appropriate size for a 10 year old. There's a detailed sizing chart for Silva at the top of the page (
http://www.compasspoint-online.co.uk/acatalog/Club...). Hopefully, Trimtex has the equivalent somewhere easy to find online.
Sorry to be pointing you to Europe rather than North American vendors but Gale's site seems to be inaccessible, Bermans don't run a full e-commerce site, etc. - verifying prices at Letro Sport and The Compass Point was quicker. I also looked at Ultrasport's site but they didn't seem to have any tops at the moment.