The following chart shows a list of every right-handed Bloodborne weapon and its generally similar Elden Ring counterparts in order to mimic how it looks and its transformation. The notes column details anything you might want to do to be more accurate or limitations. Some trick weapons have multiple potential weapons you could use, but it all comes down to your own preferance.

For most of the bloodtinge weapons, 99% of them can't be mimicked because there's no guns in Elden Ring, however, you can attempt to mimic them by putting glintstone pebble on them as an AoW

Similarity is on a 1-5 scale
1=Barely Any Similarity
2=Vague Similarity
3=Close Enough
4=Similar
5=Extremely Similar

Since Elden Ring has no guns, this section will not include every offhand weapon. Most of these come down to crossbows or the jar cannon, with the shields being somewhat similar. When possible, always put no skill on your offhand weapon in order to use Bloodhound's Step or Quickstep with your main weapon.

For Hunter Tools, your best bet is to mimic the Executioner's Gloves as there's an item that's a downgrade of it, but most of the other hunter tools can be mimicked mechnically or visually to some degree.

For armors, there's plenty to pick and choose from, but some specific sets like the Confessor, Leather, Night's Cavalry, and Raptor's set are all good options to mix and match for fashion. Some notable hats are the Aristocrat Hat along with the Mushroom Crown, Black Dumpling, and Black Wolf Mask for the unique hat and transformations from Old Hunters.

In a nutshell, Elden Ring has plenty of ways to let you mimic a lot of Bloodborne weapons, but when it comes to guns and hunter's tools its obviously lacking because of the medieval setting. I hope this helps anyone planning their bloodborne cosplay character or build.