What about Craigslist? I scored a hard-to-find item (a Burley Piccolo) by setting up a Craigslist alert, so I got an email as soon as one became available. You can also, I think, set up alerts for ebay.
If you're super-impatient, well, Burleys and Chariots have good resale value, so you could buy new and then sell it when they outgrow. My casual observation is that Burleys have more cargo room, a disadvantage that could be easily overcome with Wahl baskets. I find that I can put a few grocery bags in the "trunk" of my Burley.
Another option: Your five-year-old is getting a little big for a double trailer. My two, ages 3 and 4, complain often and loudly about being squished. Plus, double trailers generally have a weight limit of 100 pounds for kids and cargo, so now that the two of them together are 80 pounds, I'm running out of grocery room (so I shop when Big Brother is at preschool). You might consider getting a trail a bike instead of or in addition to a double trailer and towing the trailer behind that. It's long, but a lot of people do it. I wanted to, but I am too short (seat is too low) to attach one to my seat post.
And why are you looking for a double stroller? If you really walk too far for the kid, can't you get something like a buggy board to go behind it so the kiddo can stand if he gets tired? I'm picturing this kind of thing: http://www.amazon.com/Englacha-Plastic-Board-Rider-Black/dp/B0045Y1F4W. I have never used one, so I guess research carefully :-).
Good luck with the search and have fun walking and biking :-).
Thanks for all the advice :-)
Kijiji is canada's craigslist. Craigslist's around here is barely used at all, kijiji is the best place for second-hand everything. I've been looking, so far not too much available.
I've noticed lack of cargo room with our chariot, I wasn't sure how normal that was.. good to know!
My 5yr old is pretty petite at 35lbs, and little bro is 26lbs, I don't foresee the weight being an issue for awhile- we do have a trail a bike for her that attaches to the dh's bike. I'm pretty short as well, and though I haven't tried it on my bike, I know my seat post is at the bottom too... hmm. My daughter sort of likes the trail a bike, but isn't crazy about it, maybe by next summer? We lived in the country her entire life, so she's really not used to navigating all the traffic, curbs, parking lots etc, it's a bit scary for her to be on her own bike when she's not used to the surroundings.
As for the stroller, what I'm looking for is a convertible trailer that doubles as a stroller. I like walking more than biking tbh, but the dh likes biking- so we need something that works for both. I doubt I will be pushing my 5 yr old around in it as a stroller, but when I walk to the grocery or farmer's market, I want the extra space a double provides for cargo. Although, if in the middle of winter, my dd wants to snuggle in there with her bro on the way home from school the option exists.
Clear as mud? :-)
I've been looking at the Instep rocket 11, it has good reviews but the price difference between amazon.com and amazon.ca is nutso crazy. $215 on .com, $700 on .ca !!?!!