You're unlikely to find this complete, and it is a borderline platformer, but Rubble Saver is a surprisingly fun game.
There is also a Rubble Saver II that is even harder to find.
I just checked ebay and holy cow! the only copies available are $100+
In 2008 I paid $5 for a complete copy of part one, and in January of this year, after 4 years of searching, i lucked onto a complete copy of RSII for $24
Also, btw, i just read the review in Gamefaqs regarding Rubble Saver II, and I say it is spot on. However his criticism about the game being only 30-40 minutes long is really a "plus" in my book ~ this a portable game with no save feature, the length is perfect, and the challenge is high.