IS THE 500 COMPATIBLE WITH AN OUTSIDE 128 RAM STICK

HEY A QUICK QUESTION REGARDING UPGRADING MEMORY.
128 MB RAM
NOW I UNDERSTAND THAT THE SAME RAM STICK USED FOR THE 1000 OR 2500 IS COMPATIBLE.
I WENT TO A WALGREENS & INSTEAD OF BUYING AN AKAI 2GB FLASHCARD THAT WAS TO ME OVERPRICED I WENT TO WALGREENS & PURCHASED ONE FOR CHEAPER & WORKS PERFECTLY WITH NO HASSLE.

BUT WHAT IF I WAS TO LOOK AT A BEST BUY OR CIRCUIT CITY OR A LOCAL COMPUTER STORE ARE THERE ANY OUT THERE THAT WOULD BE CONSIDERED TO FULFILL THE SAME TASK AS IF I BOUGHT IT FROM AKAI...

LET ME KNOW PLEASE BEFORE I MAKE ANY MOVES.
IF YOU CAN GIVE ME SOME DETAILS ABOUT THE RAM STICK THAT IS COMPATIBLE...

THANKS..