I really dont think you will find an eighty dollar multimeter with USB. You will certainly have to purchase it online, and I dont think retail is going to happen for that price. Ebay is the only thing I can think of.
If we go with a well-known brand (Fluke) one of the few meters I could find on their website with serial and USB support was the 789. It sells for just about the same price as its model number.
http://www.newark.com/jsp/disp...%20789||S|b|4122585766
Others were in the 8800 series and were just as expensive.
Little tip: I used to work for Tektronix and I used a lot of test equipment. I have to be completely honest here. You wont get ANYTHING with a data port for 80 bucks, unless its well-used and the seller happens to be a close personal friend of yours and owes you a huge favor.
The absolute cheapest is a 287:
http://www.testequipmentdepot....iLSviJsCFWNM5QodnhjBpQ
And its almost 300 bucks, which is to be expected.