Here's a quick list of the accessories:

Rad Wagon 4:
Hardshell bags:
http://www.amazon.com/gp/product/B07Y...
Seat:
https://www.amazon.com/gp/product/B00...
Panniers:
http://www.amazon.com/gp/product/B01M...
Rear Seat w/backrest:
http://www.walmart.com/ip/BikeRearS...
Hollywood Fork mount:
http://www.amazon.com/gp/product/B000...
Handle bar extender:
http://www.amazon.com/gp/product/B06V...
Electric horn:
http://www.amazon.com/gp/product/B07D...
Clarion speaker:
http://www.ebay.com/itm/BLACKPortabl...
Front Bracket for bottle holders:
https://mridenver.com/shop/ols/produ...

Trailer:
Battery:
http://www.amazon.com/gp/product/B00M...
Lights:
http://www.amazon.com/gp/product/B014...
http://www.amazon.com/gp/product/B07C...
http://www.amazon.com/gp/product/B07S...
Controller for light sequencing:
http://www.amazon.com/gp/product/B019...
Home Depot tool box:
http://www.homedepot.com/p/Husky37i...