Here is a datapack that gives you a recipe for crafting your own trident. It does cost you 3 diamond swords to craft it so it's not exactly free but it will take you a whole lot less time to gather 6 diamonds than it will to kill 200+ drowned to get one used trident for free.

You can use either enchanted or plain diamond swords to make the trident. After making your first trident and learning the recipe (which calls for three plain diamond swords) you will only see the crafting recipe if you have three plain diamond swords and two sticks in your inventory. Please place the ingredients in the crafting table exactly as pictured below:



If you're needing a trident to take on guardians you might also want an easier recipe for a sea lantern. This recipe calls for 1 prismarine shard and 1 torch to make 1 sea lantern instead of the vanilla recipe which calls for 4 prismarine shards and 5 prismarine crystals for 1 sea lantern. Be sure and place the ingredients in the crafting table exactly as shown below:



I used the outstanding webpage from TheDestruc7i0n at this site: https://crafting.thedestruc7i0n.ca/
to create the recipe and get the JSon code which I then copied and pasted into the datapack. Feel free to change the recipe for your own use but please give me credit if you want to post it somewhere else. Enjoy!

If you need to know how to install a datapack to get it to work in your world (datapacks have to be installed to each game save) here is a link to a tutorial on how to install datapacks: https://www.youtube.com/watch?v=NIxorUpvqxg

To install a datapack into a realm or SMP world the technique is slightly different. Here is a link to a tutorial for that: https://www.youtube.com/watch?v=vXzmhiYo-V8

I just learned today that my datapack will not work if the Gravestone mod is being used. I do not know why this is but a work around would be to remove the Gravestone mod which would let the datapack work so that you could craft yourself a couple of tridents, then close and save your game, reinstall the Graveston mod and you should be good to go. I will investigate further and post an update if there is some way that I can modify my datapack so that it will work with Gravestone.