I don't have many of the high dollar items to maintain but for the general parts and accessories I always find the part number by whatever means but first place I go look is AMAZON.  They are my old Sears-N-Roebuck catalog.  With PRIME delivery is two days..  Shows up at the door with free delivery...  Even if the door is out in the sticks somewhere..
What a deal huh...
Just last week my ten year old weed wacker battery motor quit and AMAZON didn't really have the model I wanted so I ordered it from another internet site.   The shipping and handling was hugh even for normal shipping (2 weeks) ...   I should have known better haha...  The savings grace I guess is the local UPS and FEDX guys know where I live from all of my AMAZON orders haha
Roy Ken