Go to the Grey Pony on Rt 108 and pick up a copy of the Equiery and look in there. I would also go upstairs and check the bulletin board. But that price in that area will be REALLY difficult. I paid more than that at my neighbors house and we shared care, and she was a friend, and it was over 10 years ago.
You might see if there is anything out in the Bowie area. That may be less expensive, but farther. Still a stretch for that $$. You almost need to find a working board of sorts.
Same advice I gave you in July when you asked the same question.:?
Where is your horse now and what is the issue with that?
I agree with DancingArabian, you aren't going to find what you are looking for in your price range around here. Most places that allow you to work in exchange for things usually just let you work off an extra lesson, so it's not really saving you money, just preventing from spending on extras. My old barn does allow you to work for points and you can use them on anything, but they are way more than $300/month.