At Digikey, there was one but it didn't have a photo or drawing:https://www.digikey.com/products/en?keywords=115104-15-12.00
Here's the drawing at Amphenol's site. It seems to have a large diameter cable with stiffeners on the ends so it won't work in my application inside an electronics box: https://www.amphenolrf.com/downloads/dl/file/id/815/product/6180/115104_15_xx_xx_customer_drawing.pdf
I remembered that Custom Cables Group LLC sells just about any combination of cable ends and lengths at Amazon, but strangely the exact combination of right angle and 12" was not available. Here are some close contenders:
I was finding lots of 12" right angle BNC to right angle BNC cables but they were mostly 75 ohm cables. I discovered that the search term RG316 limited choices to 50 ohm.
This one is 6-inch: https://www.amazon.com/right-angle-Patch-Quality-Shipping/dp/B01CWJ4J4O/
Another one that is 6-inch: https://www.amazon.com/right-angle-Patch-Quality-Shipping/dp/B01CWJ4J4O/
Another breakthrough was to also search for RG174 which is a slightly thicker cable that is also 50 ohm. Have to be careful to avoid RG179 which is 75 ohm.
Finally, this one is pretty close at 11.8 inches but oddly by this time I had come up an alternate solution that didn't require right angle: https://www.amazon.com/Right-Angle-Cable-Using-RG174/dp/B01GPFWJA2/
The problem with the 12" right angle cables is that they all of course had a large block for doing the turn with, and I began to realize that the clearance inside my case was too small to accommodate two of these blocks in addition to the connector. Consequently I found a way to orient the boards in the case that would allow me to use my existing non-right angle cables. However, with this system I was short one 12" cable, and switching some cables to 8" would also help, so I went back to Amazon to look for additional BNC to BNC cables. Here are some of those links:
Interestingly, here is a 12" BNC to BNC straight RG316 cable from another company, and it doesn't seem to have quite as long a strain relief on the end: https://www.amazon.com/dp/B078SNS7C6/
