Light Fixture Shell

[20cc]

I have a 2 bulb setup and want to upgrade to a 4 bulb . Im looking to diy and use the 2 bulb i allready have instead of getting a whole new 4 bulb fixture . I am wondering where can i get a shell for a 4 bulb fixture . Just the shell . I saw catalina have them but they want an outrageous amount of money . Anyway if anyone has any suggestions or an old 4 bulb housing collecting dust and want to part with it for a reasonable amount im all ears. thanks guys