High chair with big tray?
This may be totally unhelpful since you said you wanted to order online -- BUT, if you're anywhere near an IKEA, I can't say enough good things about my Antilop high chair. The tray is a nice size, and I love that the chair is table-height so you can pull it right up to the table as an alternate option. The chair is solid plastic -- easy for wiping clean -- and a comfy bucket shape. And the whole thing's only $25 bucks! Even if it doesn't work for you, OP, just in case anyone out there is looking for a good (cheap) high chair, we love ours.
I love our high chair, it's inexpensive, "folds" small, has wheels (love being able to wheel ds everywhere in the kitchen lol), can be adjusted in many positions (up, up, down, down, back, forward), has a big tray on top of a small one... I just love it! Oh! And easy to clean!