Model originally uploaded to Thingiverse at https://www.thingiverse.com/thing:4321163.
I own an old Croozer Cargo, which is now known as the XLC Carry Van (https://www.xlc-parts.com/road/accessoires/lasten-transportanhaenger/1659/fahrradanhaenger-carry-van-bs-l03), because the new Croozer Cargo is a whole different design. I did not like the hitch on the Croozer Cargo, so I replaced it with a Weber hitch. To attach the Weber hitch I had to cut off the original part on the drawbar and drill a hole into it. This workes quite well for quite some time.
A couple of months ago, my wife and I got a Thule Chariot Cross child trailer. Thule has a its own hitch system with a ball head, which is also a pretty nice design, I think, but which is completley incompatible with the Weber hitch. So I looked around online and found out, that the ball head and the locking pin with the attachment can be purchased as spare parts. I ordered the ball head and the locking pin assembly group. So at the time of this writing and the time of my order, it was the time of the corona virus crisis (just in case someone reads this in a couple of years and wonders). Every seller online got flooded witch orders and the delivery companies almost drowned in shipping boxes. So it took almost two weeks for my parts to arrive.
I got a little impatient and thought, if I own a 3D printer, why not only print an adapter but the missing parts directly. So I designed a ball head, which you can see in the picture and the flexible part for the locking pin in Fusion 360 after measuring the original parts. You will need the original locking pin if you want to use the printed part. I printed the ball head in TPU with a 2 mm perimeters and 2 mm bottom and top layers in PETG. I did a short testdrive with a heavily loaded trailer and it did not break, but for security reasons I cannot recommend using it. After my ordered parts arrived, I used my printed adapter sleeve and the original parts from Thule.