After looking through an 800 page RV Accessories an Parts color PAPER catalog that I got at the 2012 Gillette Wyoming National Rally from their local Stalkups RV, I found the Utopia Brand 6332117 Strainer adapter that looks like what you want. A websearch on this part number came up with nothing, but I found it on Dyers RV online parts site -
http://www.dyersonline.com/utopia-1-1-2-x-1-1-4-strainer-adapter.html .
On edit: I looked closer at the Dyers RV listing and saw the name "LaSalle Bristol". I did a websearch on that name and the part number 6332117 and got a whole lot of hits of the part.
I guess these printed, large, RV parts and accessories catalogs are now a thing of the past due to production expense. There used to be a generic national production of these great catalogs that most all the local RV dealers would have their custom cover printed for. I guess the local service guys would call the wholesalers group associated with the catalog to get the parts for you. These catalogs, even if a bit old, are neat to latch onto if you find them to give you accessory and parts ideas for your rigs.