Bow Safety Chain?
 

make your own chain and then dip it in a bucket of plasti dip a couple times.

Get a solid piece of chain that will hold the boat. If it does not the damage to the boat bottom will far exceed the paint chip on the trailer. I have seen a 33 Donzi take a powder, owners comment was what would you need that for?

Dip like said, or just get a bungie and secure it so it can not flop around. I run two on mine, one to control forward, one the opposite . Chain is cheap, boat bottoms not so much.

The easiest thing to do might be to pick up a rubber coated anchor chain and cut it to length.

they make sleeve protectors for chains. Multiple different ID's available. I have seen them but never used them so, so I have no real life input. Just throwing it out there. :)

Edit in: using Chain Safety Sleeve for a search term seems to work well also,

https://cimg4.ibsrv.net/gimg/www.off...0f570a4fd8.jpg

I have seen SS cable a d a turnbuckle used .Usually one forward and one aft.

Padraig

and get a chain with an adequate rating.