My 16 month old moves around her cot a lot which is fine as she sleeps in a sleeping bag but it can distress her a fair bit when she gets herself stuck horizontally with her back against the head of the cot. I don’t want cot bumpers as I obviously know the risks but Is there a SAFE product on the market that will either keep her at the foot of the cot, ensure she stays vertical in the cot or stop her from bumping her head?

There is no product that will keep your daughter at the foot of the cot or stop her hitting her head,  that is recommended.
Sleep positioners &/or restraints are not recommended.
https://rednose.org.au/article/is-it-safe-to-use-products-designed-to-keep-baby-in-a-particular-position

It is not uncommon for babies to move a lot around the cot, & many will hit the sides or ends of the cot or appear to get stuck.

At 16 months of age, your baby is no longer at risk of Sudden Unexpected Death in Infancy (SUDI) - which includes SIDS.
SUDI does not occur after 12 months by definition.
It is important to still provide a safe sleep environment.
Most of the safety issues at this age are related to reducing the risk of your child falling if attempting to climb out of the cot.
It is still recommended that her cot remains free of soft, padded items like bumpers, pillows & doonas as they may be used to help baby climb out of cot.
https://rednose.org.au/article/at-what-age-can-i-introduce-cot-bumpers-and-pillows