I'm no electronics engineer, but is there any reason something like this wouldn't work?
http://www.ebay.com/itm/1pcs-RD16HHF1-S ... 3ce6069381
Ebay has a TON of cheap electronics which you can have shipped from China for pennies or a few dollars. With a well defined search, you should be able to track down the perfect part.
...and by the way, your MOSFET doesn't have to switch on 3.3v. If it needs more, you can always use the GPIO to switch a transistor to switch the MOSFET in something resembling a Darlington pair.
Obviously I haven't tried everything, or even any significant percentage, but what I've gotten and used so far (resistors, transistors, LEDs, various sensors, wires, breadboards, etc) have all worked great. And what I buy is usually among the cheapest per unit for a small number of units. (My definition of small depends on what I'm getting and my intended uses.)