Hi JR, and welcome aboard!
There are several options available, seeing as how most local hobby shops neglect commercial aviation subjects; I will name a few of my favorite sources:
#1 is Ebay. The last 30 or so Airliners I have purchased have been through ebay.
#2 is HobbyLinc.com https://www.hobbylinc.com/
#3 is Airline Hobby Supplies http://www.airline-hobby.com
There are other reputable sources, but these are my favorites listed in order of use.
Looking forward to having you as part of the group!
Take care,
Frank