How to clothe a long skinny baby

my daughter is 11 weeks and about to outgrow her 3 month onesies length wise. 3 month pants are way too big around her waist so she can't wear them. smaller sizes are too short. not a huge deal yet but I'm concerned for when the weather starts getting cooler. hopefully she will chunk up a bit by then but she always seems to get longer instead of wider when she has a growth spurt. so I'm looking for recommendations for clothing brands that carry the 0-3 mo size instead of just 3mo (cloud island from Target has been good but they only have a few options). any other mamas out there with long skinny babies? how do you dress them?