It is, unfortunately, just part of the price of starting a small business. ICA confidentiality agreements don't allow us to tell you who shops whom, so it is just not snotty uncooperativeness that prevents it. Folks tend to like the MSPs who shop places they like to go, so reading through the forum can give you a reasonable indicator of where to start signing up. Some MSPs list their clients or their past clients or have logos of their clients on their website to encourage other clients to sign on with them. Be aware that often those lists and logos are waaaaay out of date.
Still your best bet in getting started is going with the companies that have nationwide clients: Market Force (blue portal), Corporate Research, Maritz and Bare. You may not like the shops but it gets you some experience and some immediate work. Then check Jobslinger for MSPs that have recently had shops in your area and get signed up. If you are then still interested in shopping, settle down with a list and just grunt through it.
Some of the companies you work with will allow you to see shops in your area, state or nationwide. This allows you to begin building your own list of who is shopping whom. And while they may currently have no jobs posted for XYZ in your area, it may be that they have already been claimed for this month, or they may be quarterly shops and your area is out of rotation, or the entity that is their client has no relationship with the XYZ locations in your area.