Really this is just a post to hopefully help some poor soul who likes to google things rather than call tech support Like I had to end up doing. By the way chamberlain doesn't sell the part seperately, the device didn't have any indication of what voltage or amperage it runs at. Luckily the tech support was able to look at one in person and read the DC information for me. I also opened it up looking for different numbers and various things to see anything that would lead me to the proper volts an amps. No avail anyway here are a bunch of numbers from the PCB, and outside casing.
chamberlain internet gateway powercord
CIGBU/C
patent: 7,071,850 7,561,075
FCC ID: HBW7549
IC: 2666A-7549
132B2768-3
014D1205 RevE
Barcode
00000014650
132A2589-1
Oh yeah maybe why you're here.
DC 3.7V 0.3A
Adaptaplug size 'B'