Stop a Verizon truck and see if they will give you one
I just removed a Verizon-installed attenuator from my HD-DVR, it suddenly started causing some channels to not work. It is a 6 dB 5-2050 MHz ASKA brand attenuator, "made in China" of course. The model number appears to be FAM-6. It may not matter with a Tivo, but supposedly the wide frequency range is needed for the Verizon DVR. Here is a link to the ASKA home page: http://www.askacom.com/index.php, but I can't find the specific attenuator on their site. If you don't want to try the Verizon route you might call ASKA, or try your local electronics store.
Sorry, that is the best I can come up with.
Verizon FiOS TV, Internet, and phone
IMG 1.6.0, Build 06.89
Also try this place. It has mix bag of attenuators to help you control the pixelation problem.
Read this thread for more info on the problem.