Bryce, the BEST way to obtain a replacement valve is to call a genuine Cessna distributor such as Yingling (800.854.2647) or Hill (800-998-7832 ) ....and if you want to establish an IMMEDIATE rapport with them, ... call them with the exact Part Number, (and to really impress them include the Figure number, and Item number) from the Illustrated Parts Catalog (IPC) for your aircraft. (You can also check for surplus/NOS parts at Preferred AirParts
http://www.preferredairparts.com . See the note at the bottom of this page.)
Anytime you call a parts supplier, be certain to have the Serial Number of your aircraft handy. Serial numbers more accurately identify aircraft than "Year" models.
Any owner who involves himself in his aircraft's maintenance will find the most valuable resources available to be the Illustrated Parts Catalog and the Service Manual for their particular aircraft. You can obtain those manuals from the mfr (Cessna) or from an aftermarket vendor such as Aircraft Spruce (877-477-7823). Some IPC's are available in PDF format, a few are even found online free.
When you know your aircraft's exact model designation (F172), Serial number, and the specific part-number, and the IPC Figure and Item numbers, .... you will sound like a professional to a parts-supplier, and you will better insure that you will receive the correct part. There's nothing more frustrating than to order a part, pay the freight, anticipate getting back into the air....then opening the package three days later to find the part received is not the part you need. The IPC is your friend.
I hope the following is helpful to you, as I believe it might be the information you need:
Part Number 0511199-41, from IPC Figure 80, for Serials 46755 thru 17249554. (After all that, would you believe the Figure fails to actually assign an item number for your particular fuel valve? Other serial aircraft have item numbers, but not the particular type you photographed. HOwever, if your serial number is within the range I mentioned ...and which are described in the IPC on that illustration, .... then that is the part you need.)
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To give EVERYONE an idea of how much more helpful parts guys will be if you have your IPC, PN's, and serial numbers handy.... it took me almost
45 minutes to look all this information up and post this message. (and parts-guys get hundreds of requests each day,...I only get a dozen or so.) So you can see that "popping a question" such as "Hey, what does a gadget-ma-dooky for my 170 cost? and where can I get one?" ....can be a question many parts-guys simply will put on the backburner. But having done your homework, a parts guy will more likely jump right-on your parts-order, and also you will be much more likely to get the correct part.
PS: Preferred Air Parts has 19 of them in stock. 800-433-0814