Go to USPlastics.com and look in their Plastic Fittings section. Has all sorts of hose connection systems for about 10% of what they’d go for at a racing parts store.
Cheap source for Coolshirt connectors
leggwork
#2
make sure you get the type that pull apart when tugged on (think emergency egress) as I suspect these will be mandated more and more over the next few years.
cheers,
bruce
rpob5t
#3
haven’t seen a cool shirt up close but is it a hard plastic tube? I used to play paintball competitively and we used a push tube type fitting (industry called it macro line) for most of the air lines (held upwards of 1200psi). but if its something similar to this (the threads for the fittings fit 1/8" pipe threads) McMAster-Carr also sells this for cheap prices… 
BETO
#4
Well, you could actually make your own cool-shirt system for around 1/3 the price, but it’s time consuming.