Below are a few links for your convenience.
Crosshairs.zip file includes a few different options.
Please remember to make a backup copy of your “crosshairs.spr” file in case you dont like these ones.
crosshairs.spr goes under “Yourdrive:\Program Files (x86)\Steam\SteamApps\common\Half-Life\valve\sprites” directory
Models folder contents go under “Yourdrive:\Program Files (x86)\Steam\SteamApps\common\Half-Life\valve\models” directory