Do you want to attach it to a rolly bag or do you want to pull the car seat and let the toddler ride in it when tired?
Honestly, a metal, foldable luggage cart works just as well, or better than the Gogo Travelmate, often at half or even less, the price. The Gogo is basically an overpriced luggage cart, like you can find at any luggage shop or Kmart-type store.
Use an extra bungee or the LATCH straps to secure it. Get one with a metal base. Plastic bases like those on the Gogo tend to break so get something more secure. Mine's lasted over 20 years and many car seats!
Other plus; you can use it for other purposes. I used mine a lot when moving or rearranging furniture.
The problem with anything that attaches to a rolly bag is that if you can't stow your rolly bag on board, it might get gate-checked and sent to luggage claim, which means carrying your car seat. Rolly bags are hard to stow on flights because there's just not enough room, especially on airlines that charge for bags and passengers, avoiding the fees, take everything on board.
I wouldn't have a toddler ride in a car seat attached to a rolly bag but it works great with a luggage cart.