The tried and true Channel Master is still around and you can order a bunch of their stuff direct from their website.
Amazon.com is also your friend for stuff like this, tons of it.
There seems to be no markup for this stuff, for dealers anymore. It's where ever you can get it is good. Like most things these days :(

One thing that has changed for OTA (Over-The-Air) installs over the years, is the need for an LTE filter.
[Link: channelmaster.com]
Strong cellular signals are a problem in a few locations and you need the filter to keep the AGC circuit in the OTA tuners from crushing the signals.