Installation:

1: Install this mod:
https://www.gta5-mods.com/vehicles/air-port-service-and-service-vehicles-template-pack

2: Using OpenIV with "Edit Mode" enabled, add the "a_sign_1.dds" and "a_sign_2.dds" files to "E:\SteamLibrary\steamapps\common\Grand Theft Auto V\update\x64\dlcpacks\patchday3ng\dlc.rpf\x64\levels\gta5\vehicles.rpf\sadler.ytd"

3: Find and open the "vehicles.meta" file in "E:\SteamLibrary\steamapps\common\Grand Theft Auto V\update\update.rpf\common\data\levels\gta5" and append "FLAG_HAS_LIVERY" to the Sadler's "" section