You can find some great deals on Compact Flash cards that can be used to replace the hard drive on an iPod Mini. 

 

Instructions on How to Replace an iPod Mini Hard Drive

 

Choose from this list to be sure you will get a compatible drive:

 

Sandisk Ultra II cards
Sandisk ultra III 4gb
RiDATA Pro 8GB Compact Flash (CF) Flash Card Model CFR8G-SILV
Transcend CF cards
Kingston 4gb cf 45X elite pro card (not all Kingstone cards work)
Sandisk ultra III 4gb
Peak Xtreme
A-Data CF cards
8GB Memory Corp Pro 133X CF card
16gb Peak
Lexar 2GB CF Platium II 80x

 

Use the search bar above to narrow the results down to a particular brand.