try ehobbyasia - not bad prices but shipping can be pricey if u go for the 5 day service - 10 day is cheap as well though so ur choice
but if time is an issue u may have to pay more :S
I know they aint canadian retailer but u might need to go further afield for parts like that sometimes!
other notes on ue setup - I'm running a P90 with a 455 6.04 tightbore with the unported cyllinder and stock hop-up etc - gearbox is upgraded to shoot around 425fps with that setup and the hopup rubber is still working perfectly and reliably as well - I was expecting to have to change to a soft rubber but never needed to so try it first before spending more money then u can upgrade if ur hopup is unreliable