Cosatto Sprung Deluxe Mattress - know where I can get one?

[MBB]

I've just bought a Cosatto Chantelle Bedside Cot, delivered yesterday, and didn't realise what a nightmare it was going to be to find the right size mattress. The Cosatto brochure recommends their 130 size mattress (125.5 x 64.5 x 10). Baby's Best Buys recommended the Cosatto Sprung Deluxe mattress, but I just can't find anyone who stocks it, despite having been through the list of Stockists on the Cosatto website. One shop even rang up Cosatto direct and they didn't even have any of their own mattresses! I think that the measurements given are not a standard size, but I'm not sure how far 'out' I can go? Mothercare do a non standard size at 126 x 66 but not sure if this would be ok (and they haven't got them in stock anyway). I really tried to research which would be the best mattress to get and and this helped the decision of which cot to get, but know it looks like I'm stuck with a cot with no mattress. Can anyone suggest anything? I only have 5 days to send the cot back in if thats what I have to do, but I'd rather keep it if possible.

[Janus]

I'm pretty sure this is the cot I have and I got mine from M&S about 2 years ago (they do a range of stuff from Cosatto). I got mine from M&S in Marble Arch, London, don't know if this is anywhere near you but may be worth ringing them first and going from there as it may be available on their website, etc. I think ours is the sprung mattress but it was just the one that was with the cot in the store.
Hope this may help??