There are good approaches for Elance/Upwork/oDesk if you approach the job req. correctly. There are also private agencies. I've hired account reps more often via virtual assistant agencies directly than from Elance and it's ilk, but many times I'll use that platform to isolate good candidates and then work with them on small projects to test them out.

I look at the platforms as mechanisms to help you sort out the best candidates from the also-rans. I use small projects to attract candidates and essentially pay them for real (small) projects in order to interview them via their work. Then I make sure to talk to them in the process so everyone's happy with potential future opportunities.

You can break "sales" into different channels such as phone, direct, indirect, etc. VAs have been very effective for me as account managers since that's really their job as a VA anyway.

I'm happy to discuss tactics with you.