Amazon.com is offering the standard Gameboy Advance system with E-Reader bundle for $34.99. This is the previous unit that was succeeded by the GBA SP. This bundle includes the system, 5 sample cards, and the Donkey Kong Jr-E game, but it backwards compatible with all Gameboy games so the potential library is almost endless.

Glacier Game Boy Advance with e-Reader Bundle - $34.98
Indigo Game Boy Advance with e-Reader Bundle - $34.98