Alternator Upgrade

My poor battery is already feeling the addition of a second battery and amp..... Ive found the $3-500 replacements for the alternator.... Thats too much for what i want to spend. I know that with other cars, specifically jeeps, you can trade alternators among different modles with little modification. I also know that Gm has many different vortec engines.... and knowing theyre history with changing things, probably many very similar alternator bracets. Does anyone know of a replacement like this for the blazer? Ive been looking to try and find something but havent found much...

Thanks in advance
jared

well if money is the problem, i can help. go on ebay, look up the seller "MotorCityReman". He sells HO alts. Ive been getting my alts from him for really cheap, and theyre good quality.