If you're on a really tight budget since you're saving for your vacation, you might have to compromise a bit on your requirements. For example, Cold Steel offers several knives that fit the "tough tactical folder" bill, but they aren't assisted opening. Some have thumb disks that work just like an Emerson wave, but those models are over your blae length limit and don't have tanto blades.
If you can get past the lack of AO, I think you'd be very happy with a Code 4, Recon 1 or Voyager. All three lines have models with combo edge tanto blades. The blade on the Code 4 is 3 1/2", while the other two have 4" blades. Handle material is aluminum (Code 4), G-10 (Recon-1) and Grivory which is similar to FRN (Voyager). All use the Tri-Ad lock. The Recon 1 is the most expensive of the bunch at around $75, the Code 4 follows at $60 and the Voyager is, in my opinion, quite a bargain at under $50.
I've got a couple of plain edge clip point XL Voyagers, and I'm very happy with them.