Generally speaking, many of the parts stores are staffed by very inexperienced people who haven't really got a clue. I deal with these people many times every day, and it's really frustrating to have to educate them about what they have in stock...
Lordco will have 24V bulbs, likely in stock. Napa will have them, may have to get them from their DC in Langley. Gorge Auto Parts is staffed with real old-timer car buffs and they will be very helpful too - faster and better service than standing in Lordco for hours waiting for the kid behind the counter to figure it all out. Most of the other parts stores will give you as good, or often even better pricing than Lordco on similar items (mind you, quality is highly variable among the different vendors [read: price point is not always the best thing to shop for])
If you want knowledgeable service for truck parts, P&R Western Star is great. They are just down the road (northerly direction) from Lordco in Victoria. Oh, and you could have gone to the Key2 which is right next door to all the neon and chrome (ie: don't get too dazzled by all that "big city, bright lights") at Lordco.