Don't buy stuff like ram off ebay..my 2 cents..
184-pin DDR-266 (PC2100) is what it looks like your machine needs. You need to find out the max your computer can take..I'm guessing 1GB. total.
This type of ram will be very cheap as its quite old now.
Yeh, like anything there are good brands and cheap brands.
Look around on various computer parts sites for the type I mentioned to you.
EDIT: 1GB is your max and you have 2 slots. I recommend maxing it out and getting two 512mb chips. The reason I'm not saying a single 1GB chip is because some info is leading me to believe you cant put 1gb in a single slot...only 512 per slot for total 1GB...on that machine