Target.com might have World Girl stuff. They have a lot of toys and shirts on line that they don't have in stores. Generally their shipping takes 5-7 days, but I think you can expedite. Amazon has 2 day shipping as well, but it can get pricey unless you have Prime.
Have you heard of Goldi-Blocks? They are fun and pretty popular. I think they are appropriate for a 6 year old. I know Target and Toys R Us sells them, and probably amazon too. They are like legos, sort of, but are more science related.
Target also has science experiment kits, craft kits, etc. I think Michael's recently started offering on-line orders, they didn't used to have it.