High Sierra Underseat Roller at Costco | First Look
Found this Under Seat roller at Costco by High Sierra. This is a really great deal on a personal carry item sized luggage roller suitable for Spirit Airlines; it is close enough.
The closest I found online was this: https://amzn.to/2LhmSbh
Please check your airline's policy on size and weight restrictions before you fly. These change all the time.