Depends on what you are looking for and what your budget is. I personally wear a metal ball trap device from Mature Metal called "The Jailbird". I could only recommend them if you know exactly what you are looking for though and are willing to pay for quality and precision. If you are new to chastity and don't have everything down to the 1/16th of an inch of a millimeter... you might want to look into plastic models that are modular like "The Cherry Keeper".
I am locked in Jail Bird from Mature Metal. I am very comfortable without any issues or pain. I am locked 24/7, I sleep in it, go to work, kids activities, anything. I wrote a guide that might help you to design a cock cage: https://www.chastitymansion.com/for...for-24-7-cock-cage-wearing.45079/#post-509577 Krystine Kellogg made a podcast about my cock cage guide if you are interested: https://podcasts.apple.com/us/podcast/krystines-flr-podcast/id1529833492?i=1000571210960 EP: 0241 — https://krystinekellogg.com/podcast.html
I wear (and have worn) a Jail Bird from Mature Metal for many years full time. Work, play etc with no issues. Good luck!
I know I'm only adding to the chorus of voices here, but - the mature metal jailbird really is a great device. But IMO 75% of the greatness is the service and effort they'll go through to get it "just right" for you. Genitals are all different, and getting a custom cage to fit perfectly for 24/7 wear (which is MM's goal) is definitely a "Goldicocks" scenario. Lots of back and forth and patience.