Alternatively, why not try a kinderpack koolnit? It surely fits your 17mths old as the standard size is tailored from 8mths to 3yrs old.
Toddler Tula may not fit your 17mths old yet unless he/she is pretty tall, at least 84cm to be ergonomically comfy in it. This in-between size can get a Tula Coast instead if you want to aim for a Tula. The back panel is slightly wider than a standard canvas.
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