Bed guard for cot bed

[nidge1975]

Hi, We have the Rachel cotbed from John Lewis which we have just converted into a cotbed from a cot. The mattress sits below the frame of the bed however (hopefully the attached pictures will make sense) which means the guard we bought doesn't really sit properly. The mattress should fit snugly into the frame and this is no longer the case. Can anyone recommend a bed guard which is suitable for this type of cotbed?

This is the bed guard we bought - direct.asda.com/george/baby/baby-monitors-safety-essentials/dreambaby-phoenix-folding-bedrail/050307368,default,pd.html

and this is the cotbed - www.johnlewis.com/john-lewis-partners-rachel-cotbed-white/p230700878

Many thanks