Need fuel sensor

3 wire senders are typicaly voltage output.  Yours!
1 wire senders are typically 20mA output.

If you just want to replace the sender and if it is still workiing, try to measure the signal coming off the sender.
0psi = 0.5v and  15psi = 4.5v is typical. (0.5-4.5v ) but other standards exist (0-5v), (0-10v), etc.
That would allow you to cross reference other senders.

If you want to replace everything,
Fitting the hole will be the driving factor.  Measure it!
Your gauge looks to be a 2" automotive type gauge.
An Auto Parts Store gauge could work.

ACSpruce also carries 2" and 2.25"  Fuel Pressure gauges.
The senders are usually a seperate purchase.

Thanks.

The manufacturer told me to just replace the whole 'system'; i.e., gauge and sender (sensor). Frankly, I don't want to do that if I can avoid it. The gauge works fine and is not only correctly marked, but has hi/lo LEDs installed.

The sensor is indeed voltage-based, but in order to test it's range I'd need to pull the panel, which I do not want to do until I have the replacement part (Catch 22). I can fly w/o the sensor since we just plugged the line that it connects to.

The problem is that of all the sensors out there, I have yet to see one that even looks like this one, with the barb input port.

The airframe manufacturer may not be ale to tell you who supplied the gauge/sender, but they should be able to supply you with a new one.
If you have to buy the whole set, just use the sender and shelve the gauge.

The plastic sender does not look of high quality and may not last any longer than the first making a full replacement good advice.

Th bad news is that if it truely is a 0-15psi sender, find a replacement will be nearly impossible.
0-7 and 0-35 are the common values.  0-15 is a rarity.

Your sender may very well be a 0-35 and they are just using half the range.  Who knows???

The barbed end is a non-issue. Just screw whatever babed fitting you need onto the sender.

You can open the insulation near the sender to access the wires and measure the voltage as you vary the pressure.  Air will work just as well as any thing else.  Pressure is pressure!

Alternately you can cut off the sender and and use a variable low voltgae power supply to simulate the sender to determine what the gauge wants to see.

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CORRECTION from my previous post.  
0.2 - 4.54 is the most common range.
0.5 - 4.5 is availabe but less common.

0-15 (14.5) PSI are quite common since that is 0-1 Bar. The fact that the range is on the sensor rather than the gauge indicates that the sensor is not one of the larger ranges. What perplexes me about it, and hence why I am here on this forum, is that it is plumbed to the pressure side of my 912ULS--so what is everybody else using to monitor the fuel pressure on this engine? 

I agree the sensor is cheap, but it worked fine for five years and 450 hours of run time. Now that I mention it, that could be the problem. I believe EKOLOT has gone full glass and may not have any stock left of the old analog gauge equipment. Dealing with them is a PITA as they are six hours ahead and pretty much only speak Polish.