Silver Cross Pioneer liner & foot muff

[sizethree]

Hello. I am looking for some advice on keeping my LO snug over the winter on the walk to nursery.
I have a Silver Criss Pioneer but the foot muff that is comes with is easily kicked off / wriggled out of by my 11 month old. So I'm looking to get a sheepskin liner and a fleecy footmuff. But how do I find out if they are compatible with the harness? Does anyone have the same oram and can offer some pointers? Thanks.