#2
Not really, but you can make one yourself pretty cheaply. It's basically just an A-B switching box with a horn driver speaker as the 'B' and your amp as the 'A'.

Then you simply attach a length of plastic tubing into the horn driver, and fit the whole lot into nice box. The horn driver is the only expensive component used, just make sure you buy one with the correct impedence and power handling for your amp.
#3
nope
they're all pretty expensive
Guitars:
'13 MIM Fender Strat - '05 Epi G-400
Amps:
Fender HRD - VHT Special 6 Ultra -
Jet City JCA20H - Mesa Rectifier 2x12
Pedulz:
Slash Wah - OCD v1.7 - Red Llama MKII -
Big Muff Pi - Carbon Copy - Phase 90 - Ditto Looper