First congratulations on your coming grandbaby!
Not sure what you paid for the 770 but i’m Pretty sure your bank is already broken sooooo don’t try to transport it in something not meant to take the weight and size. Where did you get the machine? Sometimes the dealer will give you a deal n the case. Also should you need to repair it, being able to say you carried it in the appropriate case helps with any warrantee.
All this being said, I bought a Toto from the JoAnns on line for about $125. And I think that might work. It’s considered a good sturdy case.
Enjoy your sewing for your grandbaby!