Narrowest harnessed booster available in Canada?

My 42" 39pounder DS1 could use a harnessed booster, what is the skinniest one that we can buy up here?

I have one Radian, but since their customer service is disappointing, I would like to avoid their products at this time.

I have a 2005 Dodge Caravan and I need to get three across.
I own: Scenaras, Nauts, one Radian and Marathons. All kids need to be FF, please. My lightest is 28lbs, and the heaviest is DS1 as above.
Even a link to measured widths would help, and I can cross reference availability. I went through the three across thread and got some ideas, I haven't tried a MA/RN/MA yet, as its been cold out. We have three vehicles and growing kids, so more boosters will be in my future anyhow. The van is my primary vehicle.
TIA.

I must ask, because your signature says "Mommy to four under four" and you are asking to have all kids FF. -- How old are your kids? Are you aware of the safety benefits of rear facing?

[ame="http://www.youtube.com/watch?v=sssIsceKd6U"]YouTube - Rear facing vs forward facing position in the car[/ame]



Here is a link to a website that us members have compiled of various measurements of various seats, but often times, it's not the size of the seat that matters, it's the shape and how well it puzzles next to another seat. http://sites.google.com/site/carseatmeasurements/

Thank you for the links. I did keep the twins RF until three months ago in Marathons on the 2nd bench, but then I cannot load the big kids in the back. We also tried RF in the third row bench, but we had a terrible time loading them through the hatch, then we couldn't see any of the kids at all, since the RF Marathons in the 2nd row blocked all vision from the driver's mirror. DS1 is 48 months, 42", 39#
DD1 is 30 months, 32", 31#
twins are 20 months, 29#, short

If we need to get a 5th seat in that van, I am now looking at getting my third seat into that 3rd row, we might need it in January-I'd get a FF toddler in the back, and put a RF infant seat, likely a Safeseat on the 2nd bench.

I was doing well, until I realized last week that DS1 is nearly at the wt limit for the scenaras which we use in the third row. My GN's are fairly wide, and now I've got to install to ensure that 100% of the seat is planted-learned that on this board.
I have lucked out in that my 2nd bench has built in seats for short drives, which is where the twins sit most of the time, longer trips are in MA's. This means I can fold the seat to load the back kids, but again, that won't last if we need an infant seat. Ugg. I am trying, I really am.

Am I complicating this?