Three agents in 6 months? And now you want to make it 4? That's a major problem.
Find an agent and stick with him/her. If you do change, interview several different agents before making a choice. Make sure he/she understands what you want and what your limitations are. Make sure he/she understands your style/manner of looking for properties.
Are you changing agents, or are they dropping you? Figure out what the problem is.
Remember, too, that the homes on the MLS are limited. If there are only a few, not in good condition, in your price range, then that's the way it is. Changing an agent isn't going to make more homes appear on the MLS. It just won't.
What you need is an agent who'll take some time with you and explain your options. As you correctly note, maybe the answer is to look in different areas. Or, as is suggested below, sometimes homes that appear in poor condition don't need that much in the way of rehab. Example, there's a community near where I live. Homes sell for about $630,000. There's a foreclosure on the market for $470,000. It needs some work on the inside--paint, new kitchen cabinets, some new flooring, etc. But it would be fully liveable with $15,000-$20,000 of repairs/rehabs. Someone could buy it, put $20,000 into it, and end up with a house for $140,000 less than the houses on the same block. But buyers are afraid of doing it. The same lesson, on a smaller scale, might work for you.
Along those lines, look into a 203k loan. It's an FHA loan that includes rehab costs in it. That way, you might be able to buy a home in poor condition and have the fix-up money included in your mortgage. Ask your Realtor about that option.
Another possibility is to do a lease-option or lease-purchase on a property. That'll open your prospects up to homes that might be on the market as rentals, so you're not competing against so many other potential buyers. Again, ask your Realtor about that.
So, don't give up. But if you've been doing something that hasn't been working (like changing agents in order to try to find homes that apparently aren't on the MLS), then change what you've been doing. Look elsewhere. Or look at homes that need some fix-up. Or look at potential lease-options and lease-purchases.
Hope that helps.