It is not stipulated that fasts be observed consecutively for one who cannot find a hadiy
Question

Is it essential for the seven days’ fasting of one who cannot find a hadiy to be observed consecutively? Or is it permissible for them to be observed separately?.
Praise be to Allah.It is permissible for the seven days mentioned in the verse (interpretation of the meaning): “and seven days after his return (to his home)” [al-Baqarah 2:196] to be observed either consecutively or separately. 
And Allah is the source of strength; may Allah send blessings and peace upon our Prophet Muhammad and his family and Companions. End quote. 
Standing Committee for Academic Research and Issuing Fatwas. 
Shaykh ‘Abd al-‘Azeez ibn ‘Abd-Allaah ibn Baaz, Shaykh ‘Abd al-Razzaaq ‘Afeefi, Shaykh ‘Abd-Allaah ibn Ghadyaan, Shaykh ‘Abd-Allaah ibn Qa’ood