Not that I needed another device to test, but this one looks interesting. What features made you decide to choose it over everything else that is out there? Seems to have had an oddly high retail price for what it was - around $600?
The actual pinout off of the DB15 connector is as follows from the user manual, but you could really use any S-Video to BNC connector if you have the original breakout cable. Luma connects to the green connector and chroma attaches to the red connector.
Osprey pinout.jpg
Doesn't particularly looks like the highest quality cable (but neither does the original), but this should work:
https://www.ebay.com/itm/167477363273
Personally, I'd just wire an S-Video cable to a fresh DB15 connector if you have some basic soldering skills.