Ebay has all type of hold back stuff for trailers.  I just bought a hand full of the to use the male end to mount low on the side of the trailer for bucket holders, so the horses will not kick over their feed buckets.

If the ones you have are riveted in just drill out the rivet and you can either use screws or rivets to reinstall.  A fairly good rivet gun will cost you anywhere from 5to 20 bucks.  I bought a $20. gun and use it all the time.  More than I thought I would.

The low priced guns, $5 - $10, particularly the flat base type with a couple of holes near the end, work well for occasional jobs. They are limited in their capability, in rivet sizing and application. They are best used on flat, accessible, surfaces with smaller diameter and length rivets.

The better ones HTB speaks of, have various screw on replaceable tips, that are used depending on the rivet shank size. The long nipple design, allows you to pull a rivet stem, when the metal surface is not smooth or whenever the actual area around the rivet is physically restricted. The handles are usually longer, affording more mechanical advantage, and an easier pulling. They are also generally built better, and the jaws won't easily strip out when pulling larger diameter, stainless or steel rivets. This is the type of gun I would recommend, the $15 - $20 type. It's one of those tools, that when first used, you wonder how you got along without it.

If you have a large project, in which perhaps hundreds of rivets will be pulled, go directly to the pneumatic type of gun. It saves your wrists, fingers and temperament. Using the tool is no more difficult than firing a small caliber pistol.

Gard

If it's an aluminum trailer, stainless screws or aluminum rivets; if it's a steel trailer, stainless or zinc coated screws, steel rivets.