Try home depot, menards, sears...
Black Point Products
Hi-Performance 2-Way Cable Splitter
Model BBV-137
1GHz/130 dB. Premium quality.
Suitable for hybrid networks. Printed board circuitry. Built-in 6 KV surge protection at all ports. "F" type connections.
This looks to be a good one because it is two way... Meaning that data can move both ways...

While you are there just talk to some one and explain the problem... Most of the time they can find a product that will work for you..
By the way I found that on home depot's site.. if you want to look at it just enter this number 303166 into the search box on the upper left hand corner..