The best and cheapest option is to use suppliers who offer international shipping and can then ship direct to your customers leaving a third party expense out of it. Dropship prices don't have much meet on the bone to start with, so getting a third party involved will usually leave you with just bare bone!
That said, I know someone in the US that might, and I mean might, be able to act as a third party for you. If you are dealing with US suppliers who won't ship internationally, then you could have them ship to him and then once a week he could then do a mail run for you during doing his normal daily business.
Let me know if you would like to discuss that option with him and I'll get him to contact you and discuss.