Er, I believe phrontist was referring to an HP
scientific calculator. Most engineers I know still have their old ones from 20 years ago

But lucky for you, HP released a new RPN scientific calculator a couple months ago that fit your needs perfectly.
Visit:
http://www.hp.com/calculators/scientific/33s/
It's $50 (so you probably CAN find it for $30 on eBay) but will be worth it.
I just put an RPN program on my Ti89+ and it works great. Though for college I may have to get that 49G+...