you can do the following. Designate the target site for gibson assembly then blast the surrounding sequences in approx 100bp or less (to avoid getting hits to the backbone) and look at the results if they match a region that is downstream of a stop codon indicating that it could be a terminator. If you want to avoid all the hassle you could just add it as a another fragment in your assembly (just make sure you do not add such a large amount that are homologous to the genome because then you might get recombination at that site. I could not find the sequence of your vector, however, it is based on pMS81 and the sequence of pMS82 is available from addgene (which only differs from pMS81 in the orientation of hygR).