Warning: more shameless promotion
A very talented friend of mine recently uprooted and in Germany now sews these lovely, quality backpacks.
She makes them in a range of sizes (age dependent), and will make something to order should you have something specific in mind (flowers, butterflies etc). She can make boy ones too (trains, balls etc). She will make a sample of your idea for you with no purchase obligation.
If you are interested, please email her at dicremer at gmail dot com or leave me a note in the comments and she will get back to you. She ships all over the world.