Fred, I purchased my upgrade parts from ( U BLAST in Melbourne 0397024115 )
The air/sand mixing elbow ( p/n PB-SBC420 ) which mounts to the bottom trapdoor was $30
The foot pedal p/n ( PB-SBFP ) cost me $80
The new gun assembly which is fitted with a ceramic nozzle p/n ( PB-SBGO2 ) cost $70
I fitted 12mm hose direct from compressor. I also lowered the mesh floor in the cabinet to give me more room inside, fitted a better light and hooked up an old vacuum using one of those cheap Chinese vortex things into a 20ltr container, this traps most of the dust from the cabinet before it reaches the vac.
U Blast gave me the best price back in March 2017, but if you can buy from Amazon their prices are so much cheaper.
Zane