I am not sure how big can we go for if you need a travel stroller, but remember the lighter / more compact it will be, and also the cheaper, the less of a chance of a really upright seat. From my experience, Joie strollers, the mid-sized and larger-sized ones, are not too expensive but rather upright, so maybe the Joie Litetrax could work for you (but it is not 90 degrees).
Also, the Peg-Pérego Booklet is on the more upright side.
The Mamas&Papas Airo is boasting one of the most upright seats, travel-strollers-wise, so perhaps good to check that up, too. The reversible Eezy S-Twist2 by Cybex is also one of the upright ones.
Remember, it is also about the seat depth and overall design, so the best is to try before buying.