The key to finding parts, is using the oem part number. There is one on ebay:
Water Temperature Coolant Gauge International 353868R91 53690R2 369849R91 393476 | eBay And many more out there on the net, that include the sending unit. Unless the glass is broken in yours, it may be the sending unit. Although I have to work either of mine to get the needle to move up into the upper end of the 'cold" on the dial. The original part # for the gauge is 353868R91. A lot of the older part numbers have been superseded, or replaced by newer numbers, as is the case for this gauge, which is now 536960R2. Copy and paste the part number to a good search engine, and you're bound to find some hits. I have the best luck using Google.
Anytime you need a part for your Super C, go here (Hope the link carries through) :
(SUPER C) - FARMALL TRACTOR (1/51-12/53) | Messick's I've already got you to the Super C online catalog. Just select a section, of where you think the part you're looking for may be. As for the gauges, it is located in the chassis section, page (096).
The great thing about using Messicks, is that it shows the price at the dealer. And that should be at any Case/IH dealer in the U.S. If you don't have a dealer close, or prefer not to deal with the local dealer,and prefer another too far to drive to, you can always set up a credit card acct., and they will ship to you. I can't drive to the dealer, for what UPS charges to deliver. If I break down making hay, and they have the part in stock, it's a different story. My dealer happens to be within 2 miles of a dandy Rural King store, and several times, I've killed two birds with one stone. It does pay to check dealer prices, as some parts/items are less expensive for the OEM part.