Tissue paper is great for blotting. You can cut a package into small rectangles and it will last a good while, plus it's dirt cheap.

Rinse your wash with water only at work when you feel it oily.

You could get clean and clear oil blotting sheets. They may be a little expensive for a small pack, but they work really good, my skin feels a hundred times cleaner after using them

Blotting sheets and tissue paper work super well. If I don't have either of those things, I just use kleenex or toilet paper, but I press gently since they seem to soak up quite a bit. If I blot too often with kleenex, I might agitate my combo skin area so I just watch that.

Also, if you're not wearing any acne products or make up of any kind (if you've ever gone that route) I would maybe keep a bottle of a really mild alcohol free toner handy. I have sensitive oily skin, so I have to keep toners on the lighter side. If I'm make up free for a day, sometimes just a few quick swipes on the t-zone help and it won't dry my combo areas.

Water too. Splash of cold water and gently pat with a towel is great idea.