Schutt makes XS and 2XS models (look at a 5.6 and others) and unless your having to match a teams color I would go that route. They have universal fit/pad kits as well for like $10-15 bucks that are generic brand.
Depending on the age and organization, the straps may be mandatory. I've had umps at some tournaments make them put them on, so keep a spare handy in case.