I have one that straps to the chair for my daughter...you can use a tray with it or scoot it up to the table.
But I also have a "cooshie booshie" which has been fantastic for this transition time. She is now three and we are using it more and more. She thinks she's so big and wants to sit in a chair like her brothers which she is completely capable of doing but she has many more spills when she's not in a booster.
The cooshie booshie doesn't have straps to keep the child secured so you will want to make sure your child has good table manner and sits still before he/she is ready for this. It's rubbery material and grips to the chair. All 3 of my kids used it around the age of 2ish and it has been great!
I got it at babiesrus.
Hope this helps!
Kasey