Done a bit of searching,the rears are M7,the original is about 30mm long in total but has a large cap head,pro-bolt do M7 bolts for seatposts but theyre 20mm threaded from underside of caphead,ive compaired the 2 and its only about 2mm less than the original bolt.
Its up to you if you want to order 1 bolt and see if it fits,im 90% sure it will be fine but like i said its your call,heres the links:
Theyre available in standard Ti finish or blue/gold coloured,go to cycle parts-loose items and theyre at the bottom