look for macrogen or BGI. i worked with both, and i prefer macrogen. also, i would recommend using illumina technology.
if shipping is a problem, look for some lab that use this services to send the samples together
how long are those mRNA sequences? depending on this, you'll need larger or shorter reading sequences. always use pair end sequencing for RNA (maybe a bit expensive, but you will be thankfull when perform de bioinformatic analysis)
most important question is how deep do you want to go? (or how much money would you like to spend)
also is important to keep in mind the bioinformatic analysis. but there is a lot of free (or super cheap) tools/services