Battery/ESC tray. If you call Mike he can work something out that will work perfectly.
http://www.rc-monster.com/proddetail...MFPbatterytray
I just got a custom one with the mudgard clearance. He can make custom sizes with esc mounts though just have to ask.
I don't know which servo you are using so I can not get a link for the horn. I use Racers edge horns. Always a good fit and good quality.
http://www.amainhobbies.com/index.ph...&filter_mfr=22