Just bought our Macleren Triumph (hubby liked it better than Volo) - we love it! We purchased at The Right Start in Michigan, and there was a Combi stroller (I think) that went up to 45 lbs, so Maclaren is the only stroller that goes up to 55lbs., but there is at least one other one that goes up to 45 lbs - it was only $50.00 as well - brand new for '06.
Sorry I couldn't give more specific description as my DD 2.5 is crawling up my arms to DIS - LOL!, but if you go on their website, you should be able to find it.
A word of caution though for people using online baby vendors to do research, many of them (The Right Start, Albee Baby, etc.) have the wrong max weights listed - for example, they have 2005 & 2006 Triumps listed to a max weight of 40lbs. I've been in contact with them several times, and they insist I'm wrong, so I sent a copy of email from Maclaren (I emailed Maclaren to tell them that many of their vendors were incorrect on their websites) as well as quote from my Triumph manual.
Always contact the stroller manufacturer by email or phone for specific instructions, but your best bet based on your child's age and weight is a Maclaren - fabulous strollers!!
Good luck, Tiger