This is TXD workshop Link:
http://www.gtagarage.com/mods/show.php?id=8320
This is the place you find a Crosshair that you like:
http://crosshairs.cali-kartell.de/
Steps To Install a Crosshair and use it
●Open TXD Workshop Application
●On the top you could see a word saying"Open TXD" Click on it
●After that Locate your Gta File >Models>Hud.Txd
●Once you open that file crosshair will be the second thing
●Go to the crosshair site and pick your crosshair
●then go Back to TXD workshop And on the crosshair Press IMPORT
●Locate Your Crosshair and afterwards Click Save TXD
●Enjoy
Hope I helped
I know there is another thread but the other one is outdated
(Ss will be uploaded as soon as I get to pc)