Advice for where to post an SMS vendor competition?

I am looking for guidance on holding a vendor competition to select a text message platform for an education campaign based here in the US:

– Where would be a good place to post the RFP so that all of the various technology companies, particularly those with an education focus, would see it?
– Do you know of any top technology trade journals where RFPs are typically posted?

It is important that this is an open, published competition.

I greatly appreciate any insights you might have and look forward to hearing from you!