I've had good service from http://www.m4products.com/ for the bulbs. I re-fitted all my fluorescent myself with products from Amazon. You can get replacement LED Tubes to replace yourself, but they're expensive especially if you have as many fluorescents as I do (9 2-tube fixtures).
I can send you the info on the Amazon parts if you like. It's really rather easy, and there are How-to videos on uTube.
Mike