I have had a hard time finding items locally. For example 8 gauge crimp on connectors, in line fuses, kill switch, 40 amp circuit breaker, MC4 connectors and 12 volt connectors. For these I started with Amazon and of late have been ordering from eBay. eBay and I go back a ways but I do not use it much, it has changed dramatically in the past 5 years, not as much selling by individuals as many small stores devoted to just a few products. It seems like a lot of the small items are coming with free shipping (don't worry you are paying for it somewhere). Most comes postal service delivery and seems pretty good quality.
The larger items are always an internet purchase where I live, nothing nearby that sells solar
. Oh, I agree that Home Depot, Menards, Lowes and Farm Fleet will sell solar
items, usually a kit of some sort or you have to order it for delivery to the store. I will purchase standard battery
cables from an auto supply store, small gauge wire is expensive. For some of my wiring needs I buy a set of inexpensive jumper cables or sometimes called starter cables. Twelve feet of paired 8 gauge wire for $12.
I have used solarblvd.com and altE.com for panels and controllers. There are others.