FrazzledHunter
SILVER Star
Looks interesting as the key isn't a traditional tumbler and might be harder to pick; the pin is straight which @TeCKis300 mentioned was desirable.I use this one Hitch Locking Pin - Weigh Safe - https://www.weigh-safe.com/product/hitch-locking-pin/
It's a tight fit but I can barely get the key in and pull the lock out.
That boxed in area on either side of the receiver makes things difficult for pins with locks.