Cot bed help

[Hellohello24601]

Hi there

pregnant with my first baby and my friend has kindly offered to lend us her Maxi-Cosi Iora cot bed - but I can’t seem to find a new mattress to buy that will fit anywhere!

Does anyone have any recommendations? Also, what do people do for subsequent siblings? I know it should be a new mattress each time, but these brands only seem to sell the mattress with the cot, which seems very wasteful.

thanks