Hi Rochelle,
What kind of flute do you have now?
Are you fixing it yourself, or taking it in to a flute technician, or maybe is your band director fixing it?
It sounds to me as though maybe you need a different flute technician, if the repair does not hold. Find out from a local flute teacher or two, who have valuable flutes, whom they trust with repairing their own instrument.
If your flute won't hold a repair because it is not well made (poor metals used, poor design, etc.), then it is time for a new flute.
Your best bet on a budget is to find a re-built used flute from a reliable technician. These can be bought for around $300 U.S., which isn't too far off your budget. Check these websites:
http://www.flutestar.com Nancy Shinn works on my own flutes and piccolo, and she does an outstanding job at a really good price. She buys Yamaha 200 series flutes (among other brands) and rebuilds them to sell.
http://winds101.com Liz also has flutes reconditioned to sell, and has great deals on good student flutes.
Kara, a poster on this website, rebuilds flutes also.
If you buy a flute secondhand from the internet (or anywhere, for that matter), you will have to figure out how much money it will take to get the flute in perfect playing condition before you know the final 'cost' of the flute. (Nancy, Liz and Kara guarantee their flutes as ready to play, so that is a big hassle-remover.) Many used flutes need almost nothing done to them, and others are in need of a $250 complete overhaul. Unfortunately, the seller of the flute often really does not know what needs to be done. Your best bet is to buy a RETURNABLE used flute, send it directly to your (GOOD!) flute technician, and have him help you make the buy/send back decision.
Sometimes, someone's parents will have a good flute kept in the closet for 5 years because their child played it only 4 weeks before giving that up for, say, gymnastics. These relatively unused flutes usually need very little in terms of work to get them playing well.
Recommended flute models would include Yamaha 200 series, Pearl 500 series, Jupiter 500 series, and Trevor James. There are many other brands which might work, but you definitely want someone who a)knows flutes really well and b) is not making money from the sale of the flute, to tell you if it would be a good instrument for you.