Please help! My daughters are in a clek foonf and Chico nextfit, both rear facing in the back of my 06 Toyota Highlander. My niece is coming from overseas for two months, and I'm having real hard time to find a high back booster that fits 3 across with those other seats I have. She's 6, about 55 lbs and 46 inches, so I know technically she can be in a backless booster seat but I prefer to get a highback. Any ideas? The only one I could find was maybe clek oobr, but struggling to justify the expense for only 2 months. I might have to put a bumble in the middle seat but she never used a backless booster and that worries me for long days out and her falling asleep. Thanks in advance!